Try to answer the following questions here:

• What is this question used for?
• What does this question assess?
• What does the student have to do?
• How is the question randomised?
• Are there any implementation details that editors should be aware of?

### History and Feedback

#### Checkpoint description

Describe what's changed since the last checkpoint.

Published this.

#### Christian Lawson-Perfect2 years, 4 months ago

Gave some feedback: Ready to use

#### Christian Lawson-Perfect2 years, 4 months ago

Saved a checkpoint:

Looks good!

#### Hannah Aldous2 years, 4 months ago

Gave some feedback: Needs to be tested

#### Christian Lawson-Perfect2 years, 4 months ago

Gave some feedback: Has some problems

#### Christian Lawson-Perfect2 years, 4 months ago

Saved a checkpoint:

The marking is set up wrong: $k(-6)$ is the application of the function $k$, not $-6 \times k$. You can avoid this by writing $(\ldots)k$ instead of $k(\ldots)$.

It's not obvious what order you should enter the roots. The best I can come up with for a hint is "Assuming $k$ is positive, enter the lowest root first." I can't think how to be any clearer without giving a hint about the form of the answer.

You need \left and \right around brackets to make sure they stretch to fit around fractions.

Put the quadratic formula in the advice just before you list the values for $a$, $b$ and $c$.

#### Chris Graham2 years, 4 months ago

Gave some feedback: Has some problems

#### Chris Graham2 years, 4 months ago

When the variable C_2 is zero, your advice states $c = 0k^2$, which caused me great confusion (about where the $k^2$ had come from) when I was unlucky enough to generate this on my first attempt. If you would like to keep this scenario, then you will need to adjust the advice, or if it is not desirable then use an except in the generation of B_2 or n2.

#### Hannah Aldous2 years, 4 months ago

Gave some feedback: Needs to be tested

#### Vicky Hall2 years, 4 months ago

Gave some feedback: Has some problems

#### Vicky Hall2 years, 4 months ago

This is a well conceived question but the answers look a bit nasty! It would be a much nicer question if, when we get to the point of having $\sqrt(xk^2)$, the $x$ is a square number. That way we end up with some quantity of $k$ divided by $2$, which may or may not simplify, but it looks a lot better than having a surd or a decimal.

#### Hannah Aldous2 years, 4 months ago

Gave some feedback: Needs to be tested

#### Hannah Aldous2 years, 4 months ago

Created this as a copy of Using the Quadratic Formula to Solve Equations of the Form $ax^2 +bx+c=0$.
Using the Quadratic Formula to Solve Equations of the Form $ax^2 +bx+c=0$ Ready to use Hannah Aldous 01/08/2017 14:06
Use the quadratic formula to solve an equation in terms of an unknown variable Ready to use Hannah Aldous 01/08/2017 13:56
Katherine's copy of Using the Quadratic Formula to Solve Equations of the Form $ax^2 +bx+c=0$ draft Katherine Tomlinson 02/08/2017 12:45
Emma's copy of Using the Quadratic Formula to Solve Equations of the Form $ax^2 +bx+c=0$ draft Emma Cliffe 31/08/2017 12:59
Peter's copy of Using the Quadratic Formula to Solve Equations of the Form $ax^2 +bx+c=0$ draft Peter Knowles 12/09/2017 12:39
Using the Quadratic Formula to Solve Equations of the Form $ax^2 +bx+c=0$ [L4 Randomised] Needs to be tested Matthew James Sykes 25/07/2018 11:06
Simon's copy of Using the Quadratic Formula to Solve Equations of the Form $ax^2 +bx+c=0$ draft Simon Thomas 07/03/2019 09:55
Simon's copy of Use the quadratic formula to solve an equation in terms of an unknown variable draft Simon Thomas 07/03/2019 10:00
Use the quadratic formula to solve an equation in terms of an unknown variable draft Xiaodan Leng 11/07/2019 01:50
Solve Equations of the Form $ax^2 +bx+c=0$ draft Thomas Waters 11/09/2019 22:18
Michael's copy of Solve Equations of the Form $ax^2 +bx+c=0$ draft Michael Proudman 09/10/2019 08:25
Blathnaid's copy of Use the quadratic formula to solve an equation in terms of an unknown variable draft Blathnaid Sheridan 21/10/2019 12:19
Blathnaid's copy of Use the quadratic formula to solve an equation in terms of an unknown variable draft Blathnaid Sheridan 21/10/2019 12:33

Give any introductory information the student needs.

No variables have been defined in this question.

(a number)

Numbers between and (inclusive) with step size
A random number between and (inclusive) with step size

(text string)

(numbers)

(text strings)

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Name Type Generated Value

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Error:

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The correct answer is an equation. Use the accuracy tab to generate variable values satisfying this equation so it can be marked accurately.

#### Checking accuracy

Define the range of points over which the student's answer will be compared with the correct answer, and the method used to compare them.

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Give expressions which produce values for each of the variables in the expected answer. Leave blank to pick a random value from the range defined above, following the inferred type of the variable.

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##### Base marking algorithm

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#### Unit tests

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The following tests check that the question is behaving as desired.

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When you need to change the way this part works beyond the available options, you can write JavaScript code to be executed at the times described below.

Run this script the built-in script.

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To account for errors made by the student in earlier calculations, replace question variables with answers to earlier parts.

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These variables have some random elements, which means they're not guaranteed to have the same value each time the student submits an answer. You should define new variables to store the random elements, so that they remain the same each time this part is marked.

### Parts

Give a worked solution to the whole question.

### Preamble

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This question is used in the following exams: