1.
12a-6a^2+5-2a+3a^2=-3a^2+10a+5
2.
12a^2-9a-20a+15=12a^2-29a+15
3.
(m^2-b^2-m^2-2mb-b^2)/(mb-b^2)
(-2b^2-2mb)/(mb-b^2)
(2b(-b+m))/(b(m-b))
(2b(m-b))/(b(m-b))
2b/b
2
1.
12a-6a^2+5-2a+3a^2=-3a^2+10a+5
2.
12a^2-9a-20a+15=12a^2-29a+15
3.
(m^2-b^2-m^2-2mb-b^2)/(mb-b^2)
(-2b^2-2mb)/(mb-b^2)
(2b(-b+m))/(b(m-b))
(2b(m-b))/(b(m-b))
2b/b
2