Algebra
# Algebraic Manipulation

If $-x^3+6x^2-6x+36$ is factorized as $(a-x)(x^2+b),$ what is the value of $a+b$?

If $x+2y-6+3(1-x-2y)=-51$, what is $x+2y$?

If $x+2y=-13$, what is the value of $x^2+4xy-2x-4y-3+4y^2?$