rút gọn các biểu thưc sau ( áp dụng 7 hằng đẳng thức )
a,(2x+1).(3x-5)-(2x-1)^2-2x^2+10
b,4.(2x+3).(2x-3)-(4x+3)^2+2x+1
c,(3x+4)^2-(3x+2).(4x-5)+3x^2+11
d,(2x+1)^3-(x+2).(3x+2)^2+x^3+8
đầy đủ các bước cảm ơn + vote
đủ 4 câu vote năm sao
rút gọn các biểu thưc sau ( áp dụng 7 hằng đẳng thức ) a,(2x+1).(3x-5)-(2x-1)^2-2x^2+10 b,4.(2x+3).(2x-3)-(4x+3)^2+2x+1 c,(3x+4)^2-(3x+2).(4x-5)+3x^2
By Gianna
a, (2x+1) (3x-5) – (2x-1)²- 2x² + 10
= 6x² – 10x + 3x – 5 – (4x²- 4x + 1) – 2x²+ 10
= 6x² – 10x + 3x – 5 – 4x²+ 4x – 1 – 2x²+ 10
= -3x +4
b, 4 (2x+3) (2x-3) – (4x+3)²+ 2x + 1
= 4 (4x²- 9) – (4x+3)²+ 2x + 1
= 16x² – 36 – (16x² + 24x + 9) + 2x + 1
= 16x² – 36 – 16x² – 24x – 9 + 2x + 1
= -22x – 44
c, (3x+4)²- (3x+2) (4x-5)+3x² + 11
= 9x² + 24 +16 – (12x²- 15x + 8x – 10)+3x²+ 11
= 9x²+ 24x + 16 − 12x²+ 15x − 8x + 10 + 3x²+ 11
= 31x+37
d, (2x+1)³- (x+2) (3x+2)²+ x³+ 8
= 8x³+ 12x²+ 6x +1- (x+2) (9x²+ 12x +4)+ x³+ 8
= 8x³+ 12x²+ 6x +1− (9x³+ 12x²+ 4x + 18x²+ 24x +8)+x³+ 8
= 8x³+ 12x²+ 6x +1 − 9x³− 12x²− 4x − 18x²− 24x − 8 + x³+ 8
= −18x²− 22x + 1
– Chúc bn học tốt.
`a)(2x+1).(3x-5)-(2x-1)^2-2x^2+10`
`=6x^2-10x+3x-5-(4x^2−4x+1)-2x^2+10`
`=6x^2-10x+3x-5-4x^2+4x-1-2x^2+10`
`=-3x+4.`
`b)4.(2x+3).(2x-3)-(4x+3)^2+2x+1`
`=4.(4x^2-9)-(16x^2+24x+9)+2x+1`
`=16x^2-36-16x^2-24x-9+2x+1`
`=-22x-44.`
`c)(3x+4)^2-(3x+2).(4x-5)+3x^2+11`
`=9x^2+24x+16-(12x^2-15x+8x-10)+3x^2+11`
`=9x^2+24x+16-12x^2+15x-8x+10+3x^2+11`
`=31x+37.`
`d)(2x+1)^3-(x+2).(3x+2)^2+x^3+8 `
`=8x^3+12x^2+6x+1-(x+2)(9x^2+12x+4)+x^3+8 `
`=8x^3+12x^2+6x+1-(9x^3+12x^2+4x+18x^2+24x+8)+x^3+8 `
`=8x^3+12x^2+6x+1-9x^3-12x^2-4x-18x^2-24x-8+x^3+8 `
`=−18x^2−22x+1.`