PT
1
K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Các câu hỏi dưới đây có thể giống với câu hỏi trên
Q
21 tháng 4 2017
a) \((2x^2−3x)(5x^2−2x+1)\)
\(=2x^2.5x^2−2x^2.2x+2x^2−3x.5x^2+3x.2x−3x\)
\(=10x^4−4x^3+2x^2−15x^3+6x^2−3x\)
\(=10x^4−19x^3+8x^2−3x\)
b) \((x−2y)(3xy+5y^2+x)\)
\(=x.3xy+x.5y^2+x.x−2y.3xy−2y.5y^2−2y.x\)
\(=3x^2y+5xy^2+x^2−6xy^2−10y^3−2xy\)
\(=3x^2y−xy^2−2xy+x^2−10y^3\)
20 tháng 8 2016
Siêu dễ :
a ) \(3x\left(5x^2-2x-1\right)\)
\(=3x.5x^2-3x.2x-3x.1\)
\(=15x^3-6x^2-3x\)
b ) \(\left(x^2+2xy-3\right)\left(-xy\right)\)
\(=-xy.x^2-xy.2xy+xy.3\)
\(=-x^3y-2x^2y^2+3xy\)
IM
20 tháng 8 2016
a)
\(3x\left(5x^2-2x-1\right)\)
\(=15x^3-6x^2-3x\)
b)
\(\left(x^2+2xy-3\right)\left(-xy\right)\)
\(=-x^3y-2x^2y^2+3xy\)
28 tháng 11 2016
làm nốt
d) (2x-1)(3x+2)(3-x)
=(6x2+x-2)(3-x)
=-6x3+17x2+5x-6
e) (x+3)(x2+3x-5)
=x3+6x2+4x-15
f) (xy-2)(x3-2x-6)
=x4y-2x3-2x2y-6xy+4x+12
g) (5x3-x2+2x-3)(4x2-x+2)
=20x5-9x4+19x3-16x2+7x-6
28 tháng 11 2016
Bài 1:
a) (x-2)(x2+3x+4)
=x(5x+4)-2(5x+4)
= 5x2+4x-10x-8
=5x2-6x-8
CM
4 tháng 12 2018
a) \(\left(3x-5\right)\left(2x+3\right)-\left(2x-3\right)\left(3x+7\right)-2x\left(x-4\right)\)
\(=\left(6x^2-x-15\right)-\left(6x^2+5x-21\right)-\left(2x^2-8x\right)\)
\(=6x^2-x-15-6x^2-5x+21-2x^2+8x\)
\(=-2x^2+2x+6\)
\(=-2\left(x^2-x-3\right)\)
b) \(\left(x^2+2\right)^2-\left(x+2\right)\left(x-2\right)\left(x^2+4\right)\)
\(=\left(x^2+2\right)^2-\left(x^2-4\right)\left(x^2+4\right)\)
\(=\left(x^2+2\right)^2-\left(x^4-16\right)\)
\(=\left(x^4+4x^2+4\right)-\left(x^4-16\right)\)
\(=x^4+4x^2+4-x^4+16\)
\(=4x^2+20\)
\(=4\left(x^2+5\right)\)
c) \(\left(2x-y\right)^2-2\left(x+3y\right)^2-\left(1+3x\right)\left(3x-1\right)\)
\(=\left(4x^2-4xy+y^2\right)-2\left(x^2+6xy+9y^2\right)-\left(9x^2-1\right)\)
\(=4x^2-4xy+y^2-2x^2-16xy-18y^2-9x^2+1\)
\(=-7x^2-20xy-17y^2+1\)
d) \(\left(x^2-1\right)^3-\left(x^4+x^2+1\right)\left(x^2-1\right)\)
\(=\left(x^6-3x^4+3x^2-1\right)-\left(x^6-1\right)\)
\(=x^6-3x^4+3x^2-1-x^6+1\)
\(=-3x^4+3x^2\)
\(=-3x^2\left(x^2-1\right)\)
\(=-3x^2\left(x-1\right)\left(x+1\right)\)
e) \(\left(2x-1\right)^2-2\left(4x^2-1\right)+\left(2x+1\right)^2\)
\(=\left(2x-1\right)^2-2\left(2x-1\right)\left(2x+1\right)+\left(2x+1\right)^2\)
\(=\left[\left(2x-1\right)-\left(2x+1\right)\right]^2\)
\(=\left(2x-1-2x-1\right)^2\)
\(=\left(-2\right)^2=4\)
g) \(\left(x-y+z\right)^2+\left(y-z\right)^2-2\left(x-y+z\right)\left(z-y\right)\)
\(=\left(x-y+z\right)^2+2\left(x-y+z\right)\left(y-z\right)+\left(y-z\right)^2\)
\(=\left(x-y+z+y+z\right)^2\)
\(=\left(x+2z\right)^2\)
h) \(\left(2x+3\right)^2+\left(2x+5\right)^2-\left(4x+6\right)\left(2x+5\right)\)
\(=\left(2x+3\right)^2-2\left(2x+3\right)\left(2x+5\right)+\left(2x+5\right)^2\)
\(=\left[\left(2x+3\right)-\left(2x+5\right)\right]^2\)
\(=\left(2x+3-2x-5\right)^2\)
\(=\left(-2\right)^2=4\)
i) \(5x^2-\dfrac{10x^3+15x^2-5x}{-5x}-3\left(x+1\right)\)
\(=5x^2-\dfrac{-5x\left(-2x^2-3x+1\right)}{-5x}-3\left(x+1\right)\)
\(=5x^2-\left(-2x^2-3x+1\right)-3\left(x+1\right)\)
\(=5x^2+2x^2+3x-1-3x-3\)
\(=7x^2-4\)
CC
7 tháng 12 2019
a) \(\frac{x^2-49}{2x+1}.\frac{3}{7-x}=\frac{\left(x-7\right)\left(x+7\right)}{2x+1}.\frac{-3}{x-7}=\frac{-3\left(x-7\right)\left(x+7\right)}{\left(2x+1\right)\left(x-7\right)}=\frac{-3\left(x+7\right)}{2x+1}\)
\(=\frac{-3x-21}{2x+1}\)
b) \(\frac{3x^2-2x}{x^2-1}.\frac{1-x^4}{\left(2-3x\right)^3}=\frac{x\left(3x-2\right)}{x^2-1}.\frac{x^4-1}{\left(3x-2\right)^3}=\frac{x\left(3x-2\right)}{x^2-1}.\frac{\left(x^2-1\right)\left(x^2+1\right)}{\left(3x-2\right)^3}\)
\(=\frac{x\left(3x-2\right)\left(x^2-1\right)\left(x^2+1\right)}{\left(x^2-1\right)\left(3x-2\right)^3}=\frac{x\left(x^2+1\right)}{\left(3x-2\right)^2}=\frac{x^3+x}{\left(3x-2\right)^2}\)
SG
1
LT
20 tháng 4 2017
a) 5x2.(3x2 – 7x + 2) = 15x4 – 35x3 + 10x2
b) \(\dfrac{2}{3}\)xy( 2x2y – 3xy + y2) = \(\dfrac{4}{3}\)x3y2 – 2x2y2 + \(\dfrac{2}{3}\) xy3
RG
5 tháng 12 2018
1/ \(\frac{x-3}{3xy}\)+\(\frac{5x+3}{3xy}\)= \(\frac{6x}{3xy}\)=\(\frac{3}{y}\)
2/\(\frac{5x-7}{2x-3}\)+\(\frac{4-3x}{2x-3}\)=\(\frac{2x-3}{2x-3}\)=1
3/\(\frac{11x-7}{3-5x}\)-\(\frac{6x+4}{5x-3}\)=\(\frac{11x-7}{3-5x}\)+\(\frac{6x+4}{3-5x}\)=\(\frac{17x-3}{3-5x}\)
4/\(\frac{3}{2x+6}\)-\(\frac{x-6}{2x^2+6x}\)=\(\frac{3x}{x\left(2x+6\right)}\)-\(\frac{x-6}{x\left(2x+6\right)}\)=\(\frac{2x-6}{x\left(2x+6\right)}\)
5/\(\frac{1}{2x-10}\)+\(\frac{2x}{3x^2-15x}\)=\(\frac{1}{2\left(x-5\right)}\)+\(\frac{2x}{3x\left(x-5\right)}\)=\(\frac{3x}{6x \left(x-5\right)}\)+\(\frac{4x}{6x\left(x-5\right)}\)
=\(\frac{7x}{6x\left(x-5\right)}\)=\(\frac{7}{6\left(x-5\right)}\)
(2x2 – 3x)(5x2 – 2x + 1)
= 2x2(5x2 – 2x + 1) + (-3x)(5x2 – 2x + 1)
= 2x2.5x2 + 2x2.(-2x) + 2x2.1 + (–3x).5x2 + (-3x).(-2x) + (-3x).1
= (2.5)(x2.x2) + (2. (-2)).(x2.x) + 2x2 + [(-3).5].(x.x2) + [(-3).(-2).(x.x) + (-3x)
= 10x4 – 4x3 + 2x2 – 15x3 + 6x2 – 3x
= 10x4 – (4x3 + 15x3) + (2x2 + 6x2) – 3x
= 10x4 – 19x3 + 8x2 – 3x