Question

Expansion of (x + 3y)(x - y) gives

Answer 1

(x + 3y)(x-y)
= x (x-y) + 3y (x-y)
= x^2 -xy + 3xy -3y^2
Hope you’ll understand

Answer 2

x^2 +2xy +3y^2

Explanation:

(x + 3y)(x - y)

Foil

first x*x = x^2

outer x*-y = -xy

inner 3y^x = 3xy

last 3y*y = 3y^2

Add them together

x^2 -xy +3xy +3y^2

Combine like terms

x^2 +2xy +3y^2