Bài 1:
\(a,=-6x^7+15x^6-2x^5+x^4\\ b,=-15x^4y^7+10x^5y^6+5x^3y^5\\ c,=15x^2+20x-6x-8=15x^2+14x-8\\ d,=-x^3+x^2+x+5x^2-5x-5=-x^3+6x^2-4x-5\)
Bài 2:
\(a,=x^3+2x^2+4x+x^2+2x+4-x^3-3x^2=6x+4\\ =6\left(-\dfrac{10}{3}\right)+4=-20+4=-16\\ b,=x^2-9-x^2+x-2x+2=-x-7\\ =-\dfrac{1}{3}-7=-\dfrac{22}{3}\\ c,=\left(x-3\right)^3=\left(5-3\right)^3=2^3=8\\ d,=\left(x+y\right)\left(x^2-xy+y^2\right)-3\left(x^2-xy+y^2\right)\\ =\left(x+y-3\right)\left(x^2-xy+y^2\right)\\ =\left(3-3\right)\left(x^2-xy+y^2\right)=0\)
Đúng 2
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