Algebra
# Polynomial Arithmetic

If $x^2+20xy+100y^2=(x+ay)^2,$ what is the value of $a$?

If $x^2+121-(x-a)^2=22x,$ what is the value of $a$?

If $16x^2+56xy+49y^2=(ax+by)^2,$ what is the value of $ab$?

What is the coefficient of $x$ in the expansion of $(x+3 ) ^ 2$?