Question

How do I factor this polynomial by grouping? 2x^2 - 13x + 20

Answer 1

You don' need to grooup
what you do is
factor first term
2=1 times 2
(2x-)(x-)
they are both minus since middle term is negative
now factor other term and get the factors closest together
20=5 times 4

(2x-5)(x-4)
try it out
2x^2-5x-8x+20
2x^2-13x+20

faotred is
(2x-5)(x-4)

if you want to group you do

2 times 20=40
find what 2 numbers multiply to get 40 and add to get -13
numbers are -8 and -5
split it up
2x^2-8x-5x+20
group like factors
(2x^2-8x)+(-5x+20)
undistribute common factors
(2x)(x-4)+(-5)(x-4)
reverse distributive property ab+ac=a(b+c)
(2x-5)(x-4) 

Answer 2

2x^2-13x+20

= (2x-5) (x-4)

I hope that's help !