Iknow i have to prove that it's a parallelogram first, but how do i go about it?

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)

Common binomial factor of 6x(3x+7)+5(3x+7)

Side xy of triangle xyz is extended to point w, creating a linear pair with ∠wyz and ∠xyz. measure of an exterior angle what is the value of x? 64 80 100 180