Let's focus on #25x^3-100x^2# first. We can factor out #25x^2# from each term to get #25x^2(x-4)#. The other side, #-9x+36#, can have #-9# be factored out to give us #-9(x-4)#. Let's put our equation back together:
#25x^2(x-4)-9(x-4)#
How do we combine the binomials? Notice how #(x-4)# is a result of both parts. This will be one of our binomials. We also have #25x^2# and #-9# on the outsides of our parentheses. We'll put those two together to form our second binomial. Our answer is:
#(25x^2-9)(x-4)#
And here's a double check:
#(25x^2*x)+(25x^2*-4)+(-9*x)+(-9*-4)#
#25x^3-100x^2-9x+36# <----- Expression that we started with!
