3(2a-5b)^2-12(a-b)^2 при a =1/4 при b= -1/3

Question

3(2a-5b)^2-12(a-b)^2
при a =1/4 при b= -1/3

Answer 1

3(2a-5b)^2-12(a-b)^2=3((2a-5b)^2-(2(a-b))^2)=3(2a-5b-2a+2b)(2a-5b+2a-2b)=-9a(4a-7b)=-9*1\4(1\4*4-7*(-1\3))=-7.5