Question 6640
To find the value of c that makes {{{x^2 + 4x + c}}} a perfect square, just take the coefficient of the x-term (4), divide it by 2 and then square the result.
 {{{(4/2)^2 = 4}}}

So, the trinomial becomes: {{{x^2 + 4x + 4}}}

Now this factors into: {{{(x + 2)(x + 2)}}} or {{{(x + 2)^2}}}