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a: 3x-5>15-x
=>4x>20
hay x>5
b: \(3\left(x-2\right)\left(x+2\right)< 3x^2+x\)
=>3x2+x>3x2-12
=>x>-12
\(3x-1\le23\)
\(\Leftrightarrow3x-1+1\le23+1\)
\(\Leftrightarrow3x\le24\)
\(\Leftrightarrow x\le8\)
a,<=>3x<=24
<=>x<=8
Vậy ....
b, <=>4x-8>=9x-3-2x-1
<=>4x-9x+2x>=8-3-1
<=>-3x>=4
<=>x>=-4/3 Vậy ....
Bài 4:
a: \(=7xy\left(2-3-4\right)=-35xy\)
b: \(=\left(x-5\right)\left(x+y\right)\)
c: \(=10x\left(x-y\right)+8\left(x-y\right)=2\left(x-y\right)\left(5x+4\right)\)
d: \(=\left(x+y\right)^3-\left(x+y\right)\)
=(x+y)(x+y+1)(x+y-1)
e: =x^2+8x-x-8
=(x+8)(x-1)
f: \(=2x^2-4x+x-2=\left(x-2\right)\left(2x+1\right)\)
g: =-5x^2+15x+x-3
=(x-3)(-5x+1)
h: =x^2-3xy+xy-3y^2
=x(x-3y)+y(x-3y)
=(x-3y)*(x+y)
Bài 4:
a: \(=7xy\left(2-3-4\right)=-35xy\)
b: \(=\left(x-5\right)\left(x+y\right)\)
c: \(=10x\left(x-y\right)+8\left(x-y\right)=2\left(x-y\right)\left(5x+4\right)\)
d: \(=\left(x+y\right)^3-\left(x+y\right)\)
=(x+y)(x+y+1)(x+y-1)
e: =x^2+8x-x-8
=(x+8)(x-1)
f: \(=2x^2-4x+x-2=\left(x-2\right)\left(2x+1\right)\)
g: =-5x^2+15x+x-3
=(x-3)(-5x+1)
h: =x^2-3xy+xy-3y^2
=x(x-3y)+y(x-3y)
=(x-3y)*(x+y)
a \(2x+2>4\\ \Leftrightarrow2\left(x+1\right)>4\\ \Leftrightarrow x+1>2\\ \Leftrightarrow x>1\)
b \(3x+2>-5\\ \Leftrightarrow3x>-7\\ \Leftrightarrow x>\dfrac{-7}{3}\)
c \(10-2x>2\\ \Leftrightarrow2\left(5-x\right)>2\\ \Leftrightarrow5-x>1\\ \Leftrightarrow-x>-4\\ \Leftrightarrow x< 4\)
d \(1-2x< 3\\ \Leftrightarrow-2x< 2\\ \Leftrightarrow2x>2\\ \Leftrightarrow x>1\)
a)2x+2>4
<=> 2x>4-2
<=>2x>2
<=>x>1
Vậy...
b)3x+2>-5
<=>3x>-5-2
<=>3x>-7
<=>x>\(\dfrac{-7}{3}\)
Vậy...
c)10-2x>2
<=>-2x>-10+2
<=>-2x>-8
<=>x<4
Vậy...
d)1-2x<3
<=>-2x<3-1
<=>-2x<2
<=>x>-1
Vậy...
e)10x+3-5\(\le\)14x+12
<=>10x-2\(\le\)14x+12
<=>10x-14x\(\le\)2+12
<=>-4x\(\le\)14
<=>x\(\ge\)\(\dfrac{-7}{2}\)
Vậy...
f)(3x-1)<2x+4
<=> 3x-2x<1+4
<=>x<5
Vậy...
20) -5-(x + 3) = 2 - 5x ⇔ -5 - x - 3 = 2 -5x ⇔ 4x = 10 ⇔ x = \(\frac{5}{2}\)
Vậy...
a: 3x-5>15-x
=>3x+x>15+5
=>4x>20
=>x>5
b: \(3\left(x-2\right)\left(x+2\right)<3x^2+x\)
=>\(3\left(x^2-4\right)<3x^2+x\)
=>\(3x^2-12-3x^2-x<0\)
=>-x-12<0
=>x+12>0
=>x>-12
c: \(\left(2x+1\right)^2+3x\left(1-x\right)\le\left(x+2\right)^2\)
=>\(4x^2+4x+1+3x-3x^2\le x^2+4x+4\)
=>\(x^2+7x+1\le x^2+4x+4\)
=>7x+1<=4x+4
=>7x-4x<=4-1
=>3x<=3
=>x<=1
d: \(\frac{5x-20}{3}-\frac{2x^2+x}{2}>\frac{x\left(1-3x\right)}{3}-\frac{5x}{4}\)
=>\(\frac{4\left(5x-20\right)-6\left(2x^2+x\right)}{12}>\frac{4x\left(1-3x\right)-15x}{12}\)
=>\(4\left(5x-20\right)-6\left(2x^2+x\right)>4x\left(1-3x\right)-15x\)
=>\(20x-80-12x^2-6x>4x-12x^2-15x\)
=>14x-80>-11x
=>25x>80
=>\(x>\frac{80}{25}=\frac{16}{5}\)
e: 4-2x<=3x-6
=>-2x-3x<=-6-4
=>-5x<=-10
=>x>=2
f: \(\left(x+4\right)\left(5x-1\right)>5x^2+16x+2\)
=>\(5x^2-x+20x-4>5x^2+16x+2\)
=>19x-4>16x+2
=>3x>6
=>x>2
g: \(x\left(2x-1\right)-8<5-2x\left(1-x\right)\)
=>\(2x^2-x-8<5-2x+2x^2\)
=>-x-8<-2x+5
=>-x+2x<5+8
=>x<13
h: \(\frac{3x-1}{4}-\frac{3\left(x-2\right)}{8}-1>\frac{5-3x}{2}\)
=>\(\frac{2\left(3x-1\right)}{8}-\frac{3\left(x-2\right)}{8}-\frac88>\frac{4\left(5-3x\right)}{8}\)
=>2(3x-1)-3(x-2)-8>4(5-3x)
=>6x-2-3x+6-8>20-12x
=>3x-4>20-12x
=>15x>24
=>\(x>\frac{24}{15}\)
=>x>1,6