Question

Answer 1

7:

1: \(A=\left(x-2\right)^2-x^2+1\)

=x^2-4x+4-x^2+1

=-4x+5

=-4*21+5

=-84+5=-79

2: \(B=\left(x-1\right)\left(x-7\right)-2\left(x-3\right)\left(x-1\right)\)

=(x-1)(x-7-2x+6)

=(x-1)(-x+1)

=-(x-1)^2

=-(0-1)^2=-1

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

=2y(2x+y)

=2*(-1)(2-1)

=-2

4: \(D=x^2+2x-x-2-x^2+2x-3x\)

=-2

Answer 2

Em cần giúp bài nào nhỉ?