Answer:
c = 4
Step-by-step explanation:
In a perfect square trinomial, the following relationship is true:
[tex](x+y)^2=x^2+2xy+y^2[/tex]
In order for the given expression to be a perfect square trinomial:
[tex]x^2=x^2\\4x=2xy\\c=y^2[/tex]
Solving for 'c':
[tex]4x=2xy\\y=2\\c=y^2=2^2\\c=4[/tex]
Therefore, c must be equal to 4.
