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.
1.
1. x(x + 3) = x2 + 3x
2. 3x(x + 2) = 3x2 + 6x
3. x2(3x - 1) = 3x3 - x2
4. -5x3(x2 - 7) = -5x5 + 35x3
5. 3x(5x2 - 2x - 1) = 15x4 - 6x - 3x
6. -x2(5x3 - x - \(\dfrac{1}{2}\) ) = -5x5 + x4 - \(\dfrac{1}{2}\) x2
7. (x2 + 2x - 3) . (-x) = -x3 - 2x2 + 3x
8. 4x3 (-2x2 +4x4 - 3) = -8x5 + 16x7 - 12x
9. -5x2 (3x2 - 2x + 1) = -15x4 + 10x3 - 5x
10. -4x5(x3 - 4x2 + 7x - 3)= -47 + 16x4 - 28x6 + 15x5
11. (x + 2)(x+3)= x2 + 3x + 2x + 6
12. (x - 7)(x - 5)= x2 - 5x - 7x + 35
13. (3x + 5)(2x - 7)= 6x2 - 21x + 10x - 35
14. (x - 3)(x2 - 2x - 1)= x3 - 2x2 - x - 3x2 + 6x + 3
15. (2x - 1)(x2 - 5x + 3) = 2x3 - 10x2 + 6x - x2 + 5x - 3
16. (x - 5)(-x2 + x - 1) = -x6 + x2 - x + 5x2 - 5x + 5
17. (\(\dfrac{1}{2}\) x + 3)(2x2 - 4x - 6) = x3 - 2x2 - 3x + 6x2 - 12x - 18
2.
1. 5x2 - 3x(x + 2) = 5x2 - 3x2 - 6x = 2x2 - 6x
2. -2x2 + 3(x2 + 2) = -2x2 + 3x2 + 6 = x2 + 6
3. -4x2 + 2x - 4x(x - 5) = -4x2 + 2x -4x2 + 20x = 22x
4. 3x(x - 5) - 5x(x + 7) = 3x2 - 15x - 5x2 - 15x = -2x2
5. -3x(3x - 4) + 2x(3x + 1) = -9x + 12x + 6x + 2 = 9x - 2
6. x(x2 + x + 1) - x(2x2 + 1) = x3 + x2 + x - 2x3 - x = -x3 + x2
7. x(2x2 - 3) - x2 (5x + 1) + x2 = 2x2 - 3x - 5x3 - x2 + x2 = 2x2 - 3x - 5x3
8. 4x(x2 - x + 1) - x(3x2 - 2x - 5) = 4x4 - 4x2 + 4x - 3x3 + 2x2 + 5x = 4x4 -3x3- 2x2 + 9x
9. 4x(x2 - x + 1) + (x - 1)(x2 - x) = 4x4 - 4x2 + 4x + x3 - x2 - x2 + x = 4x4 + x3 - 2x2 +5x
