Question

The graph of y = x2 + 11x + 24 is equivalent to the graph of which equation?

y = (x + 8)(x + 3)
y = (x + 4)(x + 6)
y = (x + 9)(x + 2)
y = (x + 7)(x + 4)

Answer 1

Ax^2 +Bx + C

x^2 +11x +24

Using the number in place of C gives us what values could be inside the brackets.

For 24 the multiples are

1 and 24

2 and 12

3 and 8

4 and 6

We want the one that can add or subtract to give the number in place of B, which is 11.

The only multiples that add to 11 are 3 and 8

Therefore we know that 8 and 3 need to be in the brackets.

Giving us (x+8)(x+3)