Question

cần gấp ạ

Answer 1

2.2:

a: \(P=\left(x+1\right)^2-\left(2x-1\right)^2+3\left(x-2\right)\left(x+2\right)\)

\(=x^2+2x+1-\left(4x^2-4x+1\right)+3\left(x^2-4\right)\)

\(=x^2+2x+1-4x^2+4x-1+3x^2-12=6x-12\)

Khi x=1 thì \(P=6\cdot1-12=6-12=-6\)

b: \(Q=\left(x-3\right)\left(x+3\right)+\left(x-2\right)^2-2x\left(x-4\right)\)

\(=x^2-9+x^2-4x+4-2x\left(x-4\right)\)

\(=2x^2-4x-5-2x^2+8x=4x-5\)

Khi x=-1 thì \(Q=4\cdot\left(-1\right)-5=-4-5=-9\)

2.1:

a: \(A=\left(x+1\right)^2-\left(x+1\right)\left(x-1\right)\)

\(=x^2+2x+1-\left(x^2-1\right)\)

\(=x^2+2x+1-x^2+1=2x+2\)

b: \(B=\left(x-y\right)^2-\left(x+y\right)^2+4xy\)

\(=x^2+y^2-2xy-x^2-y^2-2xy+4xy\)

=0

c: \(C=\left(2x+3\right)\left(2x-3\right)-\left(2x-3\right)^2\)

\(=4x^2-9-\left(4x^2-12x+9\right)\)

\(=4x^2-9-4x^2+12x-9=12x-18\)