Question

What is the standard form of `y= (x + 9)(x – 1)`?

Answer 1

`y=x^2+8x-9`

Explanation:

`y=x(x-1)+9(x-1)` It is distributive!

`y=color(brown)((x xx x)) +color(blue)((x xx{ -1})) +color(red)((9xx x))+color(green)((9xx{-1}))`

`y=color(brown)(x^2)color(blue)(-x)color(red)(+9x)color(green)(-9)`

`y=x^2+8x-9`