Question

Expand and simplify (x-7)(x+3)

Answer 1

X(x+3)-7(x+3)
x2+3x-7x-21
x^2-4x-21

Answer 2

It is easy. why you didn't do it yourself?.
Anyway here is a tip to get simplified answer.
first write x*x
x^2
then multiply first x with 3 and second x with (-7) then sum up. will get 3x+(-7x) i.e (-4x). so write this.
x^2+(-4x)
and multiply (-7) by 3 i.e (-21)
x^2-4x+(-21)
So the answer will be.
x^2-4x-21