baif2 tính a, (x-8).(x^2-2x+9)+(x+1)^3 b, (2x-1)^2-3.(x-1).(x+2)-(x+3)^2 21/08/2021 Bởi Alexandra baif2 tính a, (x-8).(x^2-2x+9)+(x+1)^3 b, (2x-1)^2-3.(x-1).(x+2)-(x+3)^2
a, (x-8).(x²-2x+9)+(x+1)³ = x³- 2x²+ 9x- 8x²+ 16x- 72+ x³+ 3x²+ 3x+1 = 2x³- 7x²+ 28x- 71 b, (2x-1)²-3.(x-1).(x+2)-(x+3)² = 4x²- 4x+1 – 3(x²+x-2)- (x²+ 6x+9) = 4x²- 4x+1- 3x²- 3x+6- x²- 6x-9 = -13x-2 Bình luận
`a,(x-8)(x^2-2x+9)+(x+1)^3` `=x^3-2x^2+9x-(8x^2-16x+72)+(x+1)(x^2+2x+1)` `=x^3-2x^2+9x-8x^2+16x-72+x^3+2x^2+x+x^2+2x+1` `=(x^3+x^3)+(-2x^2-8x^2+2x^2+x^2)+(9x+16x+x+2x)+(-72+1)` `=2x^3-7x^2+28x-71` `b,(2x-1)^2-3.(x-1).(x+2)-(x+3)^2` `=4x^2-2*2x+1-3x^2-6x+3x+6-x^2-2x*3-9` `=4x^2-4x+1-3x^2-6x+3x+6-x^2-6x-9` `=(4x^2-3x^2-x^2)+(-4x-6x+3x-6x)+(1+6-9)` `=-13x-2` Bình luận
a, (x-8).(x²-2x+9)+(x+1)³
= x³- 2x²+ 9x- 8x²+ 16x- 72+ x³+ 3x²+ 3x+1
= 2x³- 7x²+ 28x- 71
b, (2x-1)²-3.(x-1).(x+2)-(x+3)²
= 4x²- 4x+1 – 3(x²+x-2)- (x²+ 6x+9)
= 4x²- 4x+1- 3x²- 3x+6- x²- 6x-9
= -13x-2
`a,(x-8)(x^2-2x+9)+(x+1)^3`
`=x^3-2x^2+9x-(8x^2-16x+72)+(x+1)(x^2+2x+1)`
`=x^3-2x^2+9x-8x^2+16x-72+x^3+2x^2+x+x^2+2x+1`
`=(x^3+x^3)+(-2x^2-8x^2+2x^2+x^2)+(9x+16x+x+2x)+(-72+1)`
`=2x^3-7x^2+28x-71`
`b,(2x-1)^2-3.(x-1).(x+2)-(x+3)^2`
`=4x^2-2*2x+1-3x^2-6x+3x+6-x^2-2x*3-9`
`=4x^2-4x+1-3x^2-6x+3x+6-x^2-6x-9`
`=(4x^2-3x^2-x^2)+(-4x-6x+3x-6x)+(1+6-9)`
`=-13x-2`