Question

What number should be added to the expression x^2 + 4x to change it into a perfect square trinomial?

Answer 1

he number that must be added is four because (x+2)^2=x^2+4x+4

Answer 2

x^2 + 4x
the number to be added is found by dividing the constant of x by 2
and squared the number
so # to be added = ( 4/2)² = 4
the perfect square trinomial is
x² + 4x + 4 = (x + 2 )² which is a perfect square trinomial
I hope this help you