Q: Thực hiện phép tính: Mn ơi ,giúp mik với ạ
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\(\dfrac{x^3-8}{x+7}\left(\dfrac{3}{x-2}-\dfrac{2}{x^2+2x+4}\right)\\ =\dfrac{\left(x-2\right)\left(x^2+2x+4\right)}{x+7}\left(\dfrac{3\left(x^2+2x+4\right)}{\left(x-2\right)\left(x^2+2x+4\right)}-\dfrac{2\left(x-2\right)}{\left(x-2\right)\left(x^2+2x+4\right)}\right)\\ =\dfrac{\left(x-2\right)\left(x^2+2x+4\right)}{x+7}\left(\dfrac{3x^2+6x+12}{\left(x-2\right)\left(x^2+2x+4\right)}-\dfrac{2x-4}{\left(x-2\right)\left(x^2+2x+4\right)}\right)\)
\(=\dfrac{\left(x-2\right)\left(x^2+2x+4\right)}{x+7}.\dfrac{3x^2+6x+12-2x+4}{\left(x-2\right)\left(x^2+2x+4\right)}\)
\(=\dfrac{3x^2+4x+16}{x+7}\)
\(=\dfrac{\left(x-2\right)\left(x^2+2x+4\right)}{x+7}\cdot\dfrac{3x^2+6x+12-2x+4}{\left(x-2\right)\left(x^2+2x+4\right)}\)
\(=\dfrac{3x^2+4x+16}{x+7}\)
\(\frac{3\left(x-2\right)}{4}\div\frac{2-x}{2}=\frac{3\left(x-2\right)}{4}\times\frac{-2}{x-2}=\frac{-3}{2}\)
học tốt
Rút gọn nhé !
\(\frac{3}{4}.\left(x-2\right):\frac{1}{2}.\left(2-x\right)=\frac{3x-6}{4}.2.\left(2-x\right)\)
\(=\frac{3x-6}{4}.\left(4-2x\right)=\frac{\left(3x-6\right).\left(4-2x\right)}{4}\)
\(=\frac{\left(12x-24\right)-\left(6x^2+12x\right)}{4}=\frac{-24-6x^2}{4}\)
\(=\frac{-12-3x^2}{2}=\frac{-3.\left(4+x^2\right)}{2}\)
\(a,=-15x^3+10x^4+20x^2\\ b,=2x^3+2x^2+4x-x^2-x-2=2x^3+x^2+3x-2\)
\(-23-150+\left(-9\right)+1913\)
\(=1913-\left(23+150+9\right)\)
\(=1913-182\)
\(=1731\)
−23 − 150 + (−9) + 1913
= -23 + (-150) + (-9) + 1913
= -(23 + 150 + 9) + 1913 = -182 + 1913 = 1913 - 182
= 1731
a, 23 + ( -77 ) + ( -23 ) + 77
= [ 23 + ( -23 ) ] + [ ( -77 ) + 77 ]
= 0 + 0 = 0
b, ( -2020 ) + 2021 + 21 + ( -22 )
= ( - 2020 ) + 2021 + 21 + ( -21 ) + ( -1 )
= [ ( -2020 ) + 2021 + ( -1 ) ] + [ 21 + ( -21 ) ]
= 0 + 0 = 0