Question

How do you solve `a^2+11a=-18`?

Answer 1

`a=-2, or -9`

Explanation:

`a^2+11a=-18`, add `18` to both sides,

`a^2+11a+18=-18+18`

`a^2+11a+18=0`, and now we try to factorize this expression,

`(a+2)(a+9)=0`,

you just have to practise playing around with these expressions to do this. We knew that the product of the real numbers must be `18`, and that the sum of their product with `a` must be `11a`. The factors `2` and `9` fulfills these criteria.