Question

Rút gọn biểu thức sau

10) (2x + 1)'2 + (-3x - 1)

11) -(x - y)'2 - (2x + y)

12) -(x + 1)'2 + (x - 1)'2

13) (2x + 7)'2 + (-2x - 3)

14) -(2x - y)'2 - (x + 3y)'2

15) -(2x + 7)'2 + (-2x - 3)'2

Answer 1

10: \(\left(2x+1\right)^2+\left(-3x-1\right)\)

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

11: \(-\left(x-y\right)^2-\left(2x+y\right)\)

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

12: \(-\left(x+1\right)^2+\left(x-1\right)^2\)

\(=-x^2-2x-1+x^2-2x+1=-4x\)

13: \(\left(2x+7\right)^2+\left(-2x-3\right)\)

\(=4x^2+28x+49-2x-3=4x^2+26x+46\)

14: \(-\left(2x-y\right)^2-\left(x+3y\right)^2\)

\(=-4x^2+4xy-y^2-x^2-6xy-9y^2\)

\(=-5x^2-2xy-10y^2\)

15: \(-\left(2x+7\right)^2+\left(-2x-3\right)^2\)

\(=-\left(4x^2+28x+49\right)+4x^2+12x+9\)

\(=-4x^2-28x-49+4x^2+12x+9=-16x-40\)