Start with
[tex]6u^2(2u-5)^2-12u^2(2u-5)(u+5)[/tex]
We can factor a 6 from both terms:
[tex]6\big(u^2(2u-5)^2-2u^2(2u-5)(u+5)\big)[/tex]
We can also factor [tex] u^2 [/tex]
[tex]6u^2\big((2u-5)^2-2(2u-5)(u+5)\big)[/tex]
Finally, both terms inside the parenthesis contain a factor of [tex] 2u-5 [/tex]
[tex]6u^2(2u-5)\big((2u-5)-2(u+5)\big)[/tex]
Finally, we can simplify the terms inside the parenthesis:
[tex]6u^2(2u-5)\big(2u-5-2u-10\big) = 6u^2(2u-5)\big(-15) = -90u^2(2u-5)[/tex]
