Question

question
re-write the quadratic function below in standard form.
$y = -9(x + 1)(x - 9)$

Explanation:

Step1: Expand the product \((x + 1)(x - 9)\)

Using the FOIL method: \((x + 1)(x - 9)=x^2-9x+x - 9=x^2-8x - 9\)

Step2: Multiply by -9

\(y=-9(x^2-8x - 9)=-9x^2+72x + 81\)

Answer:

\(y = -9x^2 + 72x + 81\)