### Instruction: Factor $36-4x^2$ completely.### Response: To factor this expression completely, I need to look for common factors, differences of squares, and other patterns that might help me.
First, I notice that both terms are multiples of 4, so I can factor out 4 from the whole expression.
That gives me $4(9-x^2)$.
Now, I see that the remaining factor is a difference of squares, since $9-x^2$ can be rewritten as $(3)^2-(x)^2$.
I recall that a difference of squares can be factored as the product of the sum and difference of the square roots, so I apply that formula here.
That gives me $4(3+x)(3-x)$.