Question

Y squared + 5y - 84 equals what

Answer 1

The two possibilities for y are y = -12 and y = 7.

In order to solve this, we first just factor the equation. In order to factor a quadratic like this, we look for factors of the last number (-84) that add up to the middle number (5). In order to find that, we just need to list the factors.

1 * -84

-1 * 84

2 * -42

-2 * 42

3 * -28

-3 * 28

4 * -21

-4 * 21

7 * -12

- 7 * 12

This last factor is the one that adds to 5. Now we stick these two numbers along with y's into parenthesis.

(y - 7)(y + 12)

Now to solve, we can set each parenthesis equal to 0 to solve.

y - 7 = 0

y = 7

y + 12 = 0

y = -12