An expression like the one seen in part h) is known as the difference of two squares, i.e. it is of the form $a^2 - b^2$. A very useful result to know is the factorisation of the difference of two squares:
\n$a^2 - b^2 = (a+b)(a-b)$
\nWe can check that this is correct:
\n$(a+b)(a-b) = a^2 + ba -ab -b^2$
\nSince multiplication is a commutative operation, i.e. the order is not important, we have that $ba = ab$, so the middle terms cancel each other out. Therefore:
\n$a^2 + ba -ab -b^2 = a^2 - b^2$
\nIt can be easy to forget about this handy result. A clue is the use of a square number you are expected to know, such as 36, 64, 81 etc. It is not always as obvious if more algebra is involved, e.g. $f^2 - g^6h^4 = (f + g^3h^2)(f-g^3h^2)$.
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\nMake sure you input an asterisk (*) for multiplication wherever necessary.
\nFor example, $xy$ should be written as $x$*$y$, and $a(b+c)$ should be written as $a$*$(b+c)$.
\nwrite $x^2$ as $x$^2
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