Bài `bb(2.2)`
`a)(3x+1)(2-3x)=0`
`3x+1=0` hoặc `2-3x=0`
`2x=-1` hoặc `3x=2`
`x=-1/2` hoặc `x=2/3`
Vậy: `S={-1/2;2/3}`
`b)(2x+1)(3x-1)=0`
`2x+1=0` hoặc `3x-1=0`
`2x=-1` hoặc `3x=1`
`x=-1/2` hoặc `x=1/3`
Vậy: `S={-1/2;1/3}`
`c)(x+5)(3x-9)=0`
`x+5=0` hoặc `3x-9=0`
`x=-5` hoặc `3x=9`
`x=-5` hoặc `x=3`
Vậy: `S={-5;3}`
`d)3x(x+7)=0`
`3x=0` hoặc `x+7=0`
`x=0` hoặc `x=-7`
Vậy: `S={0;-7}`
Bài `bb(2.7):`
`a)3x^2=48`
`x^2=48/3`
`x^2=16`
`x^2=(+-4)^2`
`x=+-4`
Vậy: `S={4;-4}`
`b)x^2+7x=0`
`x(x+7)=0`
`x=0` hoặc `x+7=0`
`x=0` hoặc `x=-7`
Vậy: `S={0;-7}`
`c)(3x+2)^2-4x^2=0`
`(3x+2)^2-(2x)^2=0`
`(3x+2-2x)(3x+2+2x)=0`
`(x+2)(5x+2)=0`
`x+2=0` hoặc `5x+2=0`
`x=-2` hoặc `5x=-2`
`x=-2` hoặc `x=-2/5`
Vậy: `S={-2;-2/5}`
`d)2x(x+6)+5(x+6)=0`
`(x+6)(2x+5)=0`
`x+6=0` hoặc `2x+5=0`
`x=-6` hoặc `2x=-5`
`x=-6` hoặc `x=-5/2`
Vậy: `S={-6;-5/2}`
Bài 1.3:
a: -6+3x=-2
=>3x=-2+6=4
=>\(x=\frac43\)
b: -2x+14=0
=>-2x=-14
=>\(x=\frac{-14}{-2}=7\)
c: \(5-\left(x+3\right)=x-2\)
=>5-x-3=x-2
=>-x+2=x-2
=>-2x=-4
=>x=2
1.5:
a: \(\frac{5x-2}{3}-\frac{5-3x}{2}=0\)
=>\(\frac{2\left(5x-2\right)-3\left(5-3x\right)}{6}=0\)
=>2(5x-2)-3(5-3x)=0
=>10x-4-15+9x=0
=>19x-19=0
=>19x=19
=>x=1
b: \(\frac{3x-1}{3}=\frac{2-x}{2}\)
=>\(2\left(3x-1\right)=3\left(2-x\right)\)
=>6x-2=6-3x
=>6x+3x=6+2
=>9x=8
=>\(x=\frac89\)
c: \(\frac{x+1}{3}+\frac{2x-5}{4}=\frac{2x-3}{12}\)
=>\(\frac{4\left(x+1\right)+3\left(2x-5\right)}{12}=\frac{2x-3}{12}\)
=>4(x+1)+3(2x-5)=2x-3
=>4x+4+6x-15=2x-3
=>10x-11=2x-3
=>8x=8
=>x=1
