// Numbas version: exam_results_page_options {"name": "Quadratic Equations: The Discriminant (Instructional)", "metadata": {"description": "

Calculate discriminant of quadratic equations and use to determine number/nature of roots.

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Calculation of quadratic discriminants.

\n

State nature of roots.

", "licence": "Creative Commons Attribution 4.0 International"}, "statement": "

Using the Quadratic Formula, the roots of a quadratic equation  \\(ax^2+ bx +c =0 \\)  are given by:

\n

\\( \\Large x=\\frac{-b \\pm \\sqrt{ \\color{red}{b^2 - 4ac}}}{2a} \\)

\n

The discriminant (\\( \\Delta \\))  is equal to the expression inside the square root (shown in red). It can be used to find the number and nature of the equation's roots.

\n

\\( \\large \\Delta = b^2 - 4ac \\)

\n

 If  \\( \\Delta > 0 \\) (positive) then the quadratic has two distinct, real roots,

\n

 If  \\( \\Delta = 0 \\) then the quadratic has one real, repeated root,

\n

 If  \\( \\Delta < 0 \\) (negative) then the roots are both non-real (complex).

", "advice": "

We are asked to rxamine a variety of quadratic equations, calculate their discriminants and then state the number and nature of their roots,

\n

\n

a)

\n

\\( \\simplify{ x^2 + {b1}x + {c1} } =0 \\)

\n

First identify the co-efficients:    \\( a = \\var{a1} \\),  \\( b = \\var{b1} \\)  and  \\( c= \\var{c1} \\).

\n

We use the formula to calculate the discriminant:

\n

\\( \\Delta = b^2 - 4ac \\)

\n

\\( \\Delta = \\var{b1}^2 - 4 \\times \\var{a1} \\times \\var{c1} \\)

\n

\\( \\Delta = \\var{disc1} \\)

\n

Since the discriminant equals zero, we can state that this equation has a single real, repeated root.

\n

 

\n

 

\n

b)

\n

\\( \\simplify{ x^2 + {b2}x + {c2} } =0 \\)

\n

First identify the co-efficients:    \\( a = \\var{a1} \\),  \\( b = \\var{b2} \\)  and  \\( c= \\var{c2} \\).

\n

We use the formula to calculate the discriminant:

\n

\\( \\Delta = b^2 - 4ac \\)

\n

\\( \\Delta = \\var{b2}^2 - 4 \\times \\var{a1} \\times \\var{c2} \\)

\n

\\( \\Delta = \\var{disc2} \\)

\n

Since the discriminant is positive, we can state that this equation has two distinct, real roots.

\n

\n

 

\n

 

\n

c)

\n

\\( \\simplify{ x^2 + {b3}x + {c3} } =0 \\)

\n

First identify the co-efficients:    \\( a = \\var{a1} \\),  \\( b = \\var{b3} \\)  and  \\( c= \\var{c3} \\).

\n

We use the formula to calculate the discriminant:

\n

\\( \\Delta = b^2 - 4ac \\)

\n

\\( \\Delta = \\var{b3}^2 - 4 \\times \\var{a1} \\times \\var{c3} \\)

\n

\\( \\Delta = \\var{disc3} \\)

\n

Since the discriminant is negative, we can state that this equation has two distinct, non-real (complex) roots.

\n

 

\n

 

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For the following quadratic equations, calculate their discriminant. Then determine the number and nature of the roots for each:

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\\( \\simplify{ x^2 + {b1}x + {c1} } =0 \\)

\n

The discriminant of this equation:   \\( \\Delta = \\)  [[0]]

\n

This equation has roots that are:

\n

[[1]]

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\\( \\simplify{ x^2 + {b2}x + {c2} } =0 \\)

\n

The discriminant of this equation:   \\( \\Delta = \\)  [[0]]

\n

This equation has roots that are:

\n

[[1]]

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\\( \\simplify{ x^2 + {b3}x + {c3} } =0 \\)

\n

The discriminant of this equation:   \\( \\Delta = \\)  [[0]]

\n

This equation has roots that are:

\n

[[1]]

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Calculation of quadratic discriminants.

\n

State nature of roots.

", "licence": "Creative Commons Attribution 4.0 International"}, "statement": "

Using the Quadratic Formula, the roots of a quadratic equation  \\(ax^2+ bx +c =0 \\)  are given by:

\n

\\( \\Large x=\\frac{-b \\pm \\sqrt{ \\color{red}{b^2 - 4ac}}}{2a} \\)

\n

The discriminant (\\( \\Delta \\))  is equal to the expression inside the square root (shown in red). It can be used to find the number and nature of the equation's roots.

\n

\\( \\large \\Delta = b^2 - 4ac \\)

\n

 If  \\( \\Delta > 0 \\) (positive) then the quadratic has two distinct, real roots,

\n

 If  \\( \\Delta = 0 \\) then the quadratic has one real, repeated root,

\n

 If  \\( \\Delta < 0 \\) (negative) then the roots are both non-real (complex).

", "advice": "

We are asked to rxamine a variety of quadratic equations, calculate their discriminants and then state the number and nature of their roots,

\n

\n

a)

\n

\\( \\simplify{ x^2 + {b2}x + {c2} } =0 \\)

\n

First identify the co-efficients:    \\( a = \\var{a1} \\),  \\( b = \\var{b2} \\)  and  \\( c= \\var{c2} \\).

\n

We use the formula to calculate the discriminant:

\n

\\( \\Delta = b^2 - 4ac \\)

\n

\\( \\Delta = \\var{b2}^2 - 4 \\times \\var{a1} \\times \\var{c2} \\)

\n

\\( \\Delta = \\var{disc2} \\)

\n

Since the discriminant is positive, we can state that this equation has two distinct, real roots.

\n

 

\n

 

\n

b)

\n

\\( \\simplify{ x^2 + {b3}x + {c3} } =0 \\)

\n

First identify the co-efficients:    \\( a = \\var{a1} \\),  \\( b = \\var{b3} \\)  and  \\( c= \\var{c3} \\).

\n

We use the formula to calculate the discriminant:

\n

\\( \\Delta = b^2 - 4ac \\)

\n

\\( \\Delta = \\var{b3}^2 - 4 \\times \\var{a1} \\times \\var{c3} \\)

\n

\\( \\Delta = \\var{disc3} \\)

\n

Since the discriminant is negative, we can state that this equation has two distinct, non-real (complex) roots.

\n

\n

 

\n

 

\n

c)

\n

\\( \\simplify{ x^2 + {b1}x + {c1} } =0 \\)

\n

First identify the co-efficients:    \\( a = \\var{a1} \\),  \\( b = \\var{b1} \\)  and  \\( c= \\var{c1} \\).

\n

We use the formula to calculate the discriminant:

\n

\\( \\Delta = b^2 - 4ac \\)

\n

\\( \\Delta = \\var{b1}^2 - 4 \\times \\var{a1} \\times \\var{c1} \\)

\n

\\( \\Delta = \\var{disc1} \\)

\n

Since the discriminant equals zero, we can state that this equation has a single real, repeated root.

\n

 

\n

 

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For the following quadratic equations, calculate their discriminant. Then determine the number and nature of the roots for each:

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\\( \\simplify{ x^2 + {b2}x + {c2} } =0 \\)

\n

The discriminant of this equation:   \\( \\Delta = \\)  [[0]]

\n

This equation has roots that are:

\n

[[1]]

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\\( \\simplify{ x^2 + {b3}x + {c3} } =0 \\)

\n

The discriminant of this equation:   \\( \\Delta = \\)  [[0]]

\n

This equation has roots that are:

\n

[[1]]

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\\( \\simplify{ x^2 + {b1}x + {c1} } =0 \\)

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The discriminant of this equation:   \\( \\Delta = \\)  [[0]]

\n

This equation has roots that are:

\n

[[1]]

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Calculation of quadratic discriminants.

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State nature of roots.

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Using the Quadratic Formula, the roots of a quadratic equation  \\(ax^2+ bx +c =0 \\)  are given by:

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\\( \\Large x=\\frac{-b \\pm \\sqrt{ \\color{red}{b^2 - 4ac}}}{2a} \\)

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The discriminant (\\( \\Delta \\))  is equal to the expression inside the square root (shown in red). It can be used to find the number and nature of the equation's roots.

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\\( \\large \\Delta = b^2 - 4ac \\)

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 If  \\( \\Delta > 0 \\) (positive) then the quadratic has two distinct, real roots,

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 If  \\( \\Delta = 0 \\) then the quadratic has one real, repeated root,

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 If  \\( \\Delta < 0 \\) (negative) then the roots are both non-real (complex).

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We are asked to rxamine a variety of quadratic equations, calculate their discriminants and then state the number and nature of their roots,

\n

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a)

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\\( \\simplify{ x^2 + {b3}x + {c3} } =0 \\)

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First identify the co-efficients:    \\( a = \\var{a1} \\),  \\( b = \\var{b3} \\)  and  \\( c= \\var{c3} \\).

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We use the formula to calculate the discriminant:

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\\( \\Delta = b^2 - 4ac \\)

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\\( \\Delta = \\var{b3}^2 - 4 \\times \\var{a1} \\times \\var{c3} \\)

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\\( \\Delta = \\var{disc3} \\)

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Since the discriminant is negative, we can state that this equation has two distinct, non-real (complex) roots.

\n

 

\n

 

\n

b)

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\\( \\simplify{ x^2 + {b1}x + {c1} } =0 \\)

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First identify the co-efficients:    \\( a = \\var{a1} \\),  \\( b = \\var{b1} \\)  and  \\( c= \\var{c1} \\).

\n

We use the formula to calculate the discriminant:

\n

\\( \\Delta = b^2 - 4ac \\)

\n

\\( \\Delta = \\var{b1}^2 - 4 \\times \\var{a1} \\times \\var{c1} \\)

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\\( \\Delta = \\var{disc1} \\)

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Since the discriminant equals zero, we can state that this equation has a single real, repeated root.

\n

 

\n

 

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c)

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\\( \\simplify{ x^2 + {b2}x + {c2} } =0 \\)

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First identify the co-efficients:    \\( a = \\var{a1} \\),  \\( b = \\var{b2} \\)  and  \\( c= \\var{c2} \\).

\n

We use the formula to calculate the discriminant:

\n

\\( \\Delta = b^2 - 4ac \\)

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\\( \\Delta = \\var{b2}^2 - 4 \\times \\var{a1} \\times \\var{c2} \\)

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\\( \\Delta = \\var{disc2} \\)

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Since the discriminant is positive, we can state that this equation has two distinct, real roots.

\n

 

\n

 

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For the following quadratic equations, calculate their discriminant. Then determine the number and nature of the roots for each:

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\\( \\simplify{ x^2 + {b3}x + {c3} } =0 \\)

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The discriminant of this equation:   \\( \\Delta = \\)  [[0]]

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This equation has roots that are:

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[[1]]

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\\( \\simplify{ x^2 + {b1}x + {c1} } =0 \\)

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The discriminant of this equation:   \\( \\Delta = \\)  [[0]]

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This equation has roots that are:

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[[1]]

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\\( \\simplify{ x^2 + {b2}x + {c2} } =0 \\)

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The discriminant of this equation:   \\( \\Delta = \\)  [[0]]

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This equation has roots that are:

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[[1]]

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