Factoring a quadratic polynomial in two variables

Question

3x^2+17xy+20y^2

Answer 1

I know if I multiply 5x4 I get 20, and that 3x4 + 5 is 17.

Answer 2

(x + 4y)(_x + 5y)

Fill the blank with the only number that works.

Note the _x^2 must equal 3x^2, and (as BobPurley has stated) 5 + 4*3 = 17