Question

Answer 1

3m-2n=4

=>2n-3m=-4

a: \(A=8mn^2-12m^2n\)

\(=4mn\cdot2n-4mn\cdot3m=4mn\left(2n-3m\right)\)

\(=4\cdot\frac{-1}{2}\cdot\left(-4\right)=\left(-2\right)\cdot\left(-4\right)=8\)

b: \(B=\left(2n-7\right)^2-2\left(2n-7\right)\left(4+3m\right)+\left(3m+4\right)^2\)

\(=\left(2n-7-3m-4\right)^2=\left(2n-3m-11\right)^2\)

\(=\left(-4-11\right)^2=\left(-15\right)^2=225\)

c: \(C=4n^2+9m^2\)

\(=\left(2n-3m\right)^2+2\cdot2n\cdot3m\)

\(=\left(-4\right)^2+12\cdot mn=16+12\cdot\frac{-1}{2}=16-6=10\)

d: \(D^2=\left(3m+2n\right)^2=9m^2+4n^2+2\cdot3m\cdot2n\)

=10+12*(-1/2)=10-6=4

=>D=2 hoặc D=-2