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\(=8x^3-36x^2+54x-27+2x^2-8x^3-29\)
\(=-34x^2+54x-56\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(B=\left(2x-1\right)^3+\left(2x+1\right)^3-2x\left(2x+1\right)\left(2x-1\right)\)
\(\Leftrightarrow B=\left(2x\right)^3-3.\left(2x\right)^2.1+3.2x.\left(1\right)^2-1^3+\left(2x\right)^3+3.\left(2x\right)^2.1+3.2x.1^2+1^3-2x\left[\left(2x\right)^2-1^2\right]\)\(\Leftrightarrow B=8x^3-12x^2+6x-1+8x^3+12x^2+6x+1-8x^3+2x\)
\(\Leftrightarrow B=8x^3+14x\)
Thay x = -2 vào B ta được:
\(B=8.\left(-2\right)^3+14.\left(-2\right)=-92\)
Vậy \(B=-92\)
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A = (x - 1)3 - x(x - 2)2 + 1
A = (x - 1)(x2 - 2x + 1) - x(x - 2)2 + 1
A = x(x2 - 2x + 1) - (x2 - 2x + 1) - x(x - 2)2 + 1
A = x3 - 2x2 + x - (x2 - 2x + 1) - x(x2 - 2x.2 + 22) + 1
A = x3 - 2x2 + x - (x2 - 2x + 1) - (x3 - 4x2 + 4x) + 1
A = x3 - 2x2 + x - x2 + 2x - 1 - x3 + 4x2 - 4x + 1
A = (x3 - x3) + (-2x2 - x2 + 4x2) + (x + 2x - 4x) + (-1 + 1)
A = x2 - x
B = (-x - 2)3 + (2x - 4)(x2 + 2x + 4) - x2(x - 6)
B = (-x - 2)[(-x2) - 2.(-x).2 + 22] + (2x - 4)(x2 + 2x + 4) - x2(x - 6)
B = -x[(-x)2 - 2.(-x).2 + 22] - 2[(-x)2 - 2.(-x).2 + 22] + (2x - 4)(x2 + 2x + 4) - x2(x - 6)
B = -(x3 + 4x2 + 4x) - (2x2 + 4x + 8) + 2x(x2 + 2x + 4) - 4(x2 + 2x + 4) - x2(x - 6)
B = -(x3 + 4x2 - 4x) - (2x2 + 4x + 8) + 2x3 + 4x2 + 8x - (x2 + 8x + 16) - (x3 - 6x2)
B = -x3 - 4x2 + 4x - 2x2 - 4x - 8 + 2x3 + 4x2 + 8x - x2 - 8x - 16 - x3 + 6x2
B = (-x3 + 2x3 - x3) + (-4x2 - 2x2 + 4x2 - x2 + 6x2) + (-4x - 8x + 8x - 8x) + (-8 - 16)
B = -12x - 24
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a.ta có
\(\left(x+3\right)^3+\left(x^2+1\right)\left(x-2\right)=x^3+9x^2+27x+27+x^3-2x^2+x-2\)
\(=2x^3+7x^2+28x+25\)
b.\(\left(2x-1\right)^2-\left(2-x\right)^3=4x^2-4x+1+x^3-6x^2+12x-8\)
\(=x^3-2x^2+8x-7\)
a) (x + 3)3 + (x2 + 1)(x - 2)
= x3 + 9x2 + 27x + 27 + x3 - 2x + x - 2
= x3 + x3 + 9x2 + 27x - 2x + x + 27 - 2
= 2x3 + 9x2 + 26x + 25
b) (2x - 1)2 - (2 - x)3
= 4x2 - 4x + 1 - ( 8 - 12x + 6x2 - x3)
= 4x2 - 4x + 1 - 8 + 12x - 6x2 + x3
= x3 + 4x2 - 6x2 + 12x - 4x + 1 - 8
= x3 - 2x2 + 8x - 7
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`Answer:`
`a)`
`A=5(x+1)^2-3(x-3)^2-4(x^2-4)`
`=>A=5(x^2+2x+1)-3(x^2-6x+9)-4x^2+16`
`=>A=5x^2+10x+5-3x^2+18x-27-4x^2+16`
`=>A=(5x^2-3x^2-4x^2)+(10x+18x)+(5-27+16)`
`=>A=-2x^2+28x-6`
`b)`
`B=5(x+1)^2-3(x-3)^2-4(x+2)(x-2)`
`=2x(3x+5)-3(3x+5)-2x(x^2-4x+4)-[(2x)^2-3^2]`
`=6x^2+10x-9x-15-2x^3+8x^2-8x-4x^2+9`
`=(6x^2-4x^2+8x^2)-2x^3+(10x-9x-8x)+(-15+9)`
Thay `x=-7` vào ta được:
`B=10(-7)^2-2(-7)^3-7(-7)-6`
`=>B=10.49-2(-343)+49-6`
`=>B=490+686+49-6`
`=>B=1219`
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=x.10x+x.7-5x.2x-5x.3+1.2x+1.3+13x\)
\(=10x^2+7x-10x^2-15x+2x+3+13x\)
\(=\left(10x^2-10x^2\right)+\left(7x-15x+2x+13x\right)+3\)
\(=0x^2+7x+3=7x+3\)
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\(A= x(10x+7)-(5x-1)(2x+3)+13x\\ = 10x^2+7x-(10x^2+15x-2x-3)+13x\\ = 10x^2+7x-10x^2-15x+2x+3+13x\\ = 7x+3\)
\(A=x.\left(10x+7\right)-\left(5x-1\right).\left(2x+3\right)+13x\)
\(A=10x^2+7x-\left(10x^2+15x-2x-3\right)+13x\)
\(A=10x^2+7x-10x^2-15x+2x+3+13x\)
\(A=\left(10x^2-10x^2\right)+\left(7x-15x+2x+13x\right)+3\)
\(A=7x+3.\)
Chúc bạn học tốt!
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a) \(\left(3x-2\right)^2-\left(2x+3\right)\left(2x-3\right)\)
\(=9x^2-12x+4-4x^2+9\)
\(=5x^2-12x+13\)
b) \(3x\left(5x-2\right)-\left(2x^2-1\right)\left(2-x\right)\)
\(=15x^2-6x-\left(4x^2-2x^3-2+x\right)\)
\(=15x^2-6x-4x^2+2x^3+2-x\)
\(=11x^2-7x+2x^3+2\)
\(\left(2x+1\right)^3-\left(2x-1\right)^3=\left(2x+1-2x+1\right)\left[\left(2x+1\right)^2+\left(2x+1\right)\left(2x-1\right)+\left(2x+1\right)^2\right]\)
\(=2.\left(4x^2+4x+1+4x^2-1+4x^2-4x+1\right)\)
\(=2\left(12x^2+1\right)\)
\(\left(2x+1\right)^3-\left(2x-1\right)^3\)
\(=\left[\left(2x\right)^3+3.\left(2x\right)^2.1+3.\left(2x\right).1^2+1^3\right]-\left[\left(2x\right)^3-3.\left(2x\right)^2.1+3.\left(2x\right).1^2-1^3\right]\)
\(=\left(8x^3+12x^2+6x+1\right)-\left(8x^3-12x^2+6x-1\right)\)
\(=8x^3+12x^2+6x+1-8x^3+12x^2-6x+1\)
\(=8x^3-8x^3+6x-6x+12x^2+12x^2+1+1\)
\(=0+0+24x^2+2\)
\(=24x^2+2\)
OK CHÚC BẠN HỌC TỐT !!!!!