Question

Which expression has been rewritten correctly to form a true statement

Answer 1

Explanation:

15

It looks like the 4th one is the one you want to investigate. There are two ways you could do it.

1. You could remove the brackets
2. You could substitute as in y^2 - 5y - 8 ie y = x^2 - 4.

I think the second way is easier to do. You will wind up with a quartic (x^4) the first way.

let y = (x^2 - 4)

Therefore z = y^2 - 5y - 6

This factors into

z = (y - 6)(y + 1)

Now put (x^2 - 4) in for y

z = (x^2 - 4 - 6)(x^2 - 4 + 1)

z = (x^2 - 10)(x^2 - 3)

So it looks like I either made the wrong guess, or I made a mistake.

Let's try the first one

Let y =x + 2

y^2+2y -8

=(y +4)(y - 2)

=(x+2 + 4)(x + 2 - 2)

=(x+ 6)(x)

Looks like the first one is the answer.