=(4x51+2x68+12x2)x7

=(204+136+24)x7

=364x7

=2548

ai trả lời hộ tui với tui cảm ơn nhiều

(4x51x7)+(2x86x7)+(12x2x7)=(204x7)+(172x7)+(24x7) =7x(204+172+24)=7x400=2800

Bài 1

1.\(x\left(x+3\right)\)

\(=x^2+3x\)

2.\(3x\left(x+2\right)\)

\(=3x^2+6x\)

3,\(x^2\left(3x-1\right)\)

\(=3x^3-x^2\)

4.\(-5x^3\left(3x^2-7\right)\)

\(=-15x^5+35x^3\)

5.\(3x\left(5x^2-2x-1\right)\)

\(=15x^3-6x^2-3x\)

6.\(-x^2\left(5x^3-x-\dfrac{1}{2}\right)\)

\(=-5x^5+x^3+\dfrac{x^2}{2}\)

7.\(\left(x^2+2x-3\right).\left(-x\right)\)

\(=-x^3-2x^2+3x\)

8.\(4x^3\left(-2x^2+4x^4-3\right)\)

\(=-8x^5+16x^7-12x^3\)

9.\(-5x^2\left(3x^2-2x+1\right)\)

\(=-15x^4+10x^3-5x^2\)

10.\(-4x^5\left(x^3-4x^2+7x-3\right)\)

\(=-4x^8+16x^7-28x^6+12x^5\)

11.\(\left(x+2\right)\left(x+3\right)\)

\(=x^2+3x+2x+6\)

12.\(\left(x-7\right)\left(x-5\right)\)

\(=x^2-5x-7x+35\)

13.\(\left(3x+5\right)\left(2x-7\right)\)

\(=6x^2-21x+10x-35\)

14.\(\left(x-3\right)\left(x^2-2x-1\right)\)

\(x^3-2x^2-x-3x^2+6x+3\)

15.\(\left(2x-1\right)\left(x^2-5x+3\right)\)

\(=2x^3-10x^2+6x-x^2+5x-3\)

16.\(\left(x-5\right)\left(-x^2+x-1\right)\)

\(=-x^3+x^2-x+5x^2-5x+5\)

17,\(\left(\dfrac{1}{2}x+3\right)\left(2x^2-4x-6\right)\)

\(=x^3-2x^2-3x+6x^2-12x-18\)

P/s:mình làm hơi tắt tại bài dài quá:))

Bài 2

1.\(5x^2-3x\left(x +2\right)\)

\(=5x^2-3x^2+2\)

\(=2x^2+2\)

2.\(-2x^2+3\left(x^2+2\right)\)

\(=-2x^2+3x^2+6\)

\(=x^2+6\)

3.\(-4x^2+2x-4x\left(x-5\right)\)

\(=-4x^2+2x-4x^2+20x\)

\(=22x\)

4.\(3x\left(x-5\right)-5x\left(x+7\right)\)

\(=3x^2-15x-5x^2-35x\)

\(=-2x^2-50x\)

5.\(-3x\left(3x-4\right)+2x\left(3x+1\right)\)

\(=-9x^2+12x+6x^2+2x\)

\(=-3x^2+14x\)

6.\(x\left(x^2+x+1\right)-x\left(2x^2+1\right)\)

\(=x^3+x^2+x-2x^3-x\)

\(=-x^3+x^2\)

7.\(x\left(2x^2-3\right)-x^2\left(5x+1\right)+x^2\)

\(=2x^3-3x-5x^3-x^2+x^2\)

\(=-3x^3-3x\)

8.\(4x\left(x^2-x+1\right)-x\left(3x-2x-5\right)\)

\(=4x^3-4x^2+4x-3x^2+2x^2+5x\)

\(=4x^3-5x^2+9x\)

9.\(4x\left(x^2-x+1\right)+\left(x-1\right)\left(x^2-x\right)\)

\(=4x^3-4x^2+4x+x^3-x^2-x^2+x\)

\(=5x^3-6x^2+5x\)

10.\(\left(2x-3\right)\left(x+4\right)+\left(-x+1\right)\left(x-2\right)\)

\(=2x^2+8x-3x-12+-x^2+2x+x-2\)

\(=x^2+8x-14\)

11.\(\left(-x+5\right)\left(x+3\right)+\left(2x-1\right)\left(x+3\right)\)

\(=-x^2-3x+5x+15+2x^2+6x-x-3\)

\(=x^2+7x+12\)

12.\(\left(x+3\right)\left(x-1\right)-4x\left(x^2-2x\right)\)

\(=x^2-x+3x-3-4x^3+8x^2\)

\(=9x^2+2x-3-4x^3\)

Bài nhiều câu như thế này lần sau bạn lưu ý tách ra các post riêng nhé.

`7,`

`a, B+A=4x-2x^2+3`

`-> B=(4x-2x^2+3)-A`

`-> B=(4x-2x^2+3)-(x^2-2x+1)`

`B=4x-2x^2+3-x^2+2x-1`

`B=(-2x^2-x^2)+(4x+2x)+(3-1)`

`B=-3x^2+6x+2`

`b, C-A=-x+7`

`-> C=(-x+7)+A`

`-> C=(-x+7)+(x^2-2x+1)`

`-> C=-x+7+x^2-2x+1`

`C=x^2+(-x-2x)+(7+1)`

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

`c,`

`A-D=x^2-2`

`-> D= A- (x^2-2)`

`-> D=(x^2-2x+1)-(x^2-2)`

`D=x^2-2x+1-x^2+2`

`D=(x^2-x^2)-2x+(1+2)`

`D=-2x+3`

`6,`

`a,`

`P+Q=4x-2x^2+3`

`-> Q=(4x-2x^2+3)-P`

`-> Q=(4x-2x^2+3)-(3x^2+x-1)`

`Q=4x-2x^2+3-3x^2-x+1`

`Q=(-2x^2-3x^2)+(4x-x)+(3+1)`

`Q=x^2+3x+4`

`b,`

`x^2-5x+2-P=H`

`-> H= (x^2-5x+2)-(3x^2+x-1)`

`H=x^2-5x+2-3x^2-x+1`

`H=(x^2-3x^2)+(-5x-x)+(2+1)`

`H=-4x^2-6x+3`

`c,`

`P-R=5x^2-3x-4`

`-> R= P- (5x^2-3x-4)`

`-> R=(3x^2+x-1)-(5x^2-3x-4)`

`R=3x^2+x-1-5x^2+3x+4`

`R=(3x^2-5x^2)+(x+3x)+(-1+4)`

`R=-2x^2+4x+3`

hong bít

= 1400 nha bn

0,2 x 317 x 7 + 0,14 x 3520 + 33,1 x 14 

= (0,2 x 7) x 317 + 0,14 x 3520 + 33,1 x 14 

= 1,4 x 317 + 0,14 x 3520 + 33,1 x 14

= 443,8 + 492,8 + 463,4

= 1400

=1,4*317+1,4*352+1,4*331=1,4*(317+331+352)=1,4*1000=1400

1D

2A

3A

4D

5B

6D

7B

8D

9B

10A

có j đâu

Có gì đâu mà gửi vậy?

= -20

-Hok tốt~

Tính nhanh hay là tính như bình thường???????

20 ạ 

Kb hem