math question help?

Question

hi i have a question, for one of my questions in algebra it says simlify each expression. Determine its value when x=7, x= -5 and x=0

9x-5-6x-2x+4 ---- the answer i got was 88 but in my book (the answers, my teacher tells us to look at the back so we know if it's right or wrong he just wants the steps from us to see if we know how to do it)

the answer it says is x -1; 6; -6; -1 why is that the answer and how can i reach that answer by simplifying?

Answer 1

When X=7...

(9 x 7) - 5 - (6 x 7) - (2 x 7) + 4=
63 - 5 - 42 - 14 + 4 =
6

When X=-5
(9 x -5) - 5 - (6 x -5) - (2 x -5) + 4=
-45 - 5 + 30 + 10 + 4=
-1

When X=0
(9 x 0) - 5 - (6 x 0) - (2 x 0) + 4=
0 - 5 - 0 - 0 + 4=
-1

Remember: a negative multiplied by a negative is a positive.

Answer 2

First simplify:

9x-5-6x-2x+4 = x-1

Do you know how I got that? Combine 9x-6x-2x =9x-8x=x
and -5+4=-1. If you can't follow that you need a quick tuition from someone in your family.

Then substitute each value of x:

when x=7, x-1= 7-1=6
when x=-5, x-1=-5-1=-6
when x=0, x-1=0-1=-1