SOLUTION: Multipy. (x - 10)(x + 9) These are so confusing to me. Please help. Thank you.

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Question 27563: Multipy. (x - 10)(x + 9)
These are so confusing to me.

Please help.
Thank you.
Answer by sdmmadam@yahoo.com(530) About Me  (Show Source):
You can put this solution on YOUR website!

(x - 10)(x + 9)
Use formula (x+a)(x+b) = x^2 +(a+b)x +ab
Here a = -10 and b = 9
Therefore (x-10)(x+9) = x^2 +(-10+9)x + (-10)X 9
= x^2 +(-1)x -90
= x^2 -x -90
Note: You may do it by direct multiplication too.