Question

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Answer 1

`1)`

`a)A=(3x-1)^2+(x+3)(2x-1)`

`A=9x^2-6x+1+2x^2-x+6x-3`

`A=11x^2-x-2`

 

`b)B=(x-2)(x^2+2x+4)-x(x^2-2)`

`B=x^3-8-x^2+2x`

`B=2x-8`

 

`c)C=(2x+y+3)(2x+y-3)-(2x+3)^2`

`C=(2x+y)^2-9-4x^2-12x-9`

`C=4x^2+4xy+y^2-4x^2-12x-9`

`C=4xy-12x-18`

 

`3)x^3+y^3=(x+y)(x^2-xy+y^2)=(x+y)[(x+y)^2-3xy]=3(3^2-3.2)=9`

Answer 2

Bài 1

\(a,A=9x^2-6x+1+\left(2x^2+6x-x-3\right)\\ =9x^2-6x+1+2x^2+5x-3\\ =11x^2-x-2\\ b,B=x^3-8-x^3+2x\\ =2x-8\\ c,C=\left(2x+y\right)^2-9-4x^2-12x-9\\ =4x^2+4xy+y^2-9-4x^2-12x-9\\ =4xy+y^2-12-18\)

Bài 2

\(a,x^3-64-x^2+6x-2=0\\ 6x-66=0\\ 6x=66\\ x=11\\ b,2x^2+x-2\left(x^2-1\right)-5=0\\ 2x^2+x-2x^2+2-5=0\\ x-3=0\\ x=3\)