To solve the quadratic equation \(4x^2 + 20x = -25\) by factoring, we first rewrite the equation in standard form:
\[ 4x^2 + 20x + 25 = 0 \]
Next, we notice that this can be factored as a perfect square trinomial. We can rewrite the left side as:
\[ (2x + 5)^2 = 0 \]
Now, we solve for \(x\) by taking the square root of both sides:
\[ 2x + 5 = 0 \]
Subtracting 5 from both sides gives:
\[ 2x = -5 \]
Now, dividing by 2:
\[ x = -\frac{5}{2} \]
Thus, the solution to the equation is:
\[ \boxed{-\frac{5}{2}} \]