7(x - 3) - x(3 - x)

= (x - 3)(7 + x)

chỉ bt có v mà k bt có đúng k 

1 ) 7 ( x - 3 ) - x ( 3 - x ) 

= 7 ( x - 3 ) + x ( x - 3 )

= ( x - 3 ) ( 7 + x )

2 ) 4x² - 6x + 3 - 2x

= 4x² - 2x - 6x + 3

= 2x ( 2x - 1 ) - 3 ( 2x - 1 )

= ( 2x - 1 ) ( 2x - 3 )

3 ) ( 4 - x ) - 4x + x²

= ( 4 - x ) - x ( 4 - x )

= ( 4 - x ) (  1 - x )

4 ) x² - 2xy + y²

= ( x - y )²

1, \(7\left(x-3\right)-x\left(3-x\right)=7\left(x-3\right)+x\left(x-3\right)\)

\(=\left(x-3\right)\left(x+7\right)\)

2,\(4x^2-6x+\left(3-2x\right)=4x^2-8x+3\)

\(=4x^2-6x-2x+3=2x\left(2x-3\right)-\left(2x-3\right)\)

\(=\left(2x-3\right)\left(2x-1\right)\)

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

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

4,\(x^2-2xy+y^2=\left(x-y\right)^2\)

\(=2.34\left(2+2\cdot2+3\cdot2-2\right)=2.34\cdot10=23.4\)

\(0,18\text{×}1230+0,9\text{×}1567\text{×}2-3\text{×}690\\ =221,4+2820,6-2070=1015\)

\(284:\left[314-\left(x+3\right)\right]=12.\)

\(\Leftrightarrow\left[314-\left(x+3\right)\right]=\frac{71}{3}\)

\(\Leftrightarrow\left(x+3\right)=\frac{871}{3}\)

\(\Leftrightarrow x=\frac{862}{3}\)

\(14.\left[251-\left(x-5\right)\right]=1470\)

\(\Leftrightarrow\left[251-\left(x-5\right)\right]=105\)

\(\Leftrightarrow x-5=146\)

\(\Leftrightarrow x=151\)

\(\left(120+x\right):x-15=16\)

\(\Leftrightarrow\left(120+x\right):x=31\)

\(\Leftrightarrow\left(120+x\right).\frac{1}{x}=31\)

\(\Leftrightarrow\frac{1}{x}.x+120x=31\)

\(\Leftrightarrow1+120x=31\)

\(\Leftrightarrow120x=30\)

\(\Leftrightarrow x=4\)

\(\left(135-x\right):x+24=28\)

\(\Leftrightarrow\left(135-x\right):x=4\)

\(\Leftrightarrow\left(135-x\right).\frac{1}{x}=4\)

\(\Leftrightarrow\frac{1}{x}.135-\frac{1}{x}x=4\)

\(\Leftrightarrow\frac{1}{x}135-1=4\)

\(\Leftrightarrow\frac{1}{x}135=5\)

\(\Leftrightarrow\frac{1}{x}=\frac{1}{27}\)

\(\Leftrightarrow x=27\)

a) |x| + |x-2| = 2 

TH1: \(x< 0\Rightarrow-x-x+2=2\Leftrightarrow-2x=0\Rightarrow x=0\)

TH2: \(0\le x< 2\Rightarrow x-x+2=0\Rightarrow0x=-2\)(PT vô nghiệm)

TH3: \(x>2\Rightarrow x+x-2=0\Rightarrow2x=2\Rightarrow x=1\)(loại vì 1<2 không thỏa mãn ĐK)

b) |x-1| + |x-4| = 3x

TH1: \(x-1\le0\Rightarrow x\le1\)

\(-x+1-x+4=3x\Leftrightarrow5-2x=3x\Leftrightarrow5x=5\Rightarrow x=1\)

TH2: \(1\le x\le4\)

\(x-1-x+4=3x\Leftrightarrow3x=3\Rightarrow x=1\)

TH3: \(x\ge4\)

\(x-1+x-4=3x\Leftrightarrow2x-5=3x\Rightarrow x=-5\)(loại vì -5<4 không thỏa mãn với ĐK)

Em cảm ơn anh ạ :))

ban chia đa thức 1 biến đã sắp xếp nha

ban chia đa thức 1 biến đã sắp xếp nha

a: =20,23(15,75+85,25-1)

=20,23*100

=2023

b: =0,66+3,34+2,8+1,2

=4+4

=8

20,23 x 15,75 + 20,23 x 85,25 - 20,23

=2023 x (15,75+85,25-1)

= 2023 x 100

=202300

0,66 + 1,2 + 3,34 + 2,8

=(0,66+3,34)+(1,2+2,8)

=4+4

=8

                                                               Bài giải

\(\frac{1}{2}\left(x+1\right)+\frac{1}{4}\left(x+3\right)=3\cdot\frac{1}{3}\cdot\left(x+20\right)\)

\(\frac{1}{2}\left[\left(x+1\right)+\frac{1}{2}\left(x+3\right)\right]=x+20\)

\(\frac{1}{2}\left[x+1+\frac{1}{2}x+\frac{3}{2}\right]=x+20\)

\(\frac{1}{2}\left[x\left(1+\frac{1}{2}\right)+1+\frac{3}{2}\right]=x+20\)

\(\frac{1}{2}\left[\frac{3}{2}x+\frac{5}{2}\right]=x+20\)

\(\frac{3}{4}x+\frac{5}{4}=x+20\)

\(\frac{3}{4}x-x=20-\frac{5}{4}\)

\(\frac{-1}{4}x=\frac{75}{4}\)

\(x=\frac{75}{4}\text{ : }\frac{-1}{4}\)

\(x=-75\)

\(\frac{1}{2}\left(x+1\right)+\frac{1}{4}\left(x+3\right)=3\cdot\frac{1}{3}\cdot\left(x+20\right)\)

\(\frac{1}{2}\left[\left(x+1\right)+\frac{1}{2}\left(x+3\right)\right]=x+20\)

\(\frac{1}{2}\left[x+1+\frac{1}{2}x+\frac{3}{2}\right]=x+20\)

\(\frac{1}{2}\left[x\left(1+\frac{1}{2}\right)+1+\frac{3}{2}\right]=x+20\)

\(\frac{1}{2}\left[\frac{3}{2}x+\frac{5}{2}\right]=x+20\)

\(\frac{3}{4}x+\frac{5}{4}=x+20\)

\(\frac{3}{4}x-x=20-\frac{5}{4}\)

\(\frac{-1}{4}x=\frac{75}{4}\)

\(x=\frac{75}{4}\text{ : }\frac{-1}{4}\)

\(x=-75\)