If (x-4)(x+9) = x² + bx + c for all values of x, what is the value of c?

Expand with FOIL: $(x - 4)(x + 9) = x^2 + 9x - 4x - 36 = x^2 + 5x - 36$. Comparing with $x^2 + bx + c$ gives $b = 5$ and $c = -36$. The question asks for $c$, which is $-36$. Shortcut: the constant term of a product of binomials is the product of the constants, $(-4)(9) = -36$. A common wrong answer is 36, from dropping the negative sign, and another is 5, which is $b$, the middle coefficient. A third is 13, from adding 4 and 9. Be sure to report the coefficient the question asks about.