Đáp án:
$e) M=-21\\
g) N=\dfrac{31}{2}\\$
Giải thích các bước giải:
$e) M = (2x + y)^2- (2x + y ) ( 2x - y ) + y(x - y )\\
=4x^2+4xy+y^2-(4x^2-y^2)+xy-y^2\\
=4x^2+4xy+y^2-4x^2+y^2+xy-y^2\\
=(4x^2-4x^2)+(4xy+xy)+(y^2+y^2-y^2)\\
=5xy+y^2\\
\Rightarrow M=5.(-2).3+3^2=-30+9=-21\\
g) N = ( a -3b)^2 - (a + 3b)^2 - (a - 1 )(b - 2 ) \\
=a^2-6ab+9b^2-(a^2+6ab+9b^2)-(ab-2a-b+2)\\
=a^2-6ab+9b^2-a^2-6ab-9b^2-ab+2a+b-2\\
=(a^2-a^2)+(9b^2-9b^2)+(-6ab-6ab-ab)+2a+b-2\\
=-13ab+2a+b-2\\
\Rightarrow N=-13.\dfrac{1}{2}.(-3)+2\dfrac{1}{2}-3-2=\dfrac{39}{2}+1-5=\dfrac{31}{2}\\$