Answer :
FOIL
x*x-4x-9x-9x(-4)
Calculate the products
X^2-4x-9x-9x(-4)
X^2-4x-9x+36
Collect like terms
X^2-13x+36
x*x-4x-9x-9x(-4)
Calculate the products
X^2-4x-9x-9x(-4)
X^2-4x-9x+36
Collect like terms
X^2-13x+36