Bài 4:
a: 5+2x=20-3x
=>5x=20-5=15
=>\(x=\dfrac{15}{5}=3\)
b: \(7-\left(2x+4\right)=-\left(x+4\right)\)
=>\(7-2x-4=-x-4\)
=>-2x+7=-x
=>-x=-7
=>x=7
c: \(\left(5x+2\right)-3\left(2x+1\right)=-3x+7\)
=>5x+2-6x-3=-3x+7
=>-x-1=-3x+7
=>2x=7+1=8
=>x=8:2=4
d: 2x-(3-5x)=4(x+3)
=>2x-3+5x=4(x+3)
=>7x-3=4(x+3)
=>7x-3=4x+12
=>3x=15
=>x=15:3=5
e: \(5\left(2x-3\right)-4\left(5x-7\right)=19-2\left(x+11\right)\)
=>\(10x-15-20x+28=19-2x-22\)
=>\(-10x+13=-2x-3\)
=>-8x=-16
=>\(x=\dfrac{-16}{-8}=2\)
f: \(x^2-\left(x+2\right)\left(x-2\right)=2x\)
=>\(x^2-\left(x^2-4\right)=2x\)
=>2x=4
=>x=2
g: \(\dfrac{1-3x}{6}+x-1=\dfrac{x+2}{2}\)
=>\(\dfrac{1-3x+6\left(x-1\right)}{6}=\dfrac{3\left(x+2\right)}{6}\)
=>1-3x+6x-6=3(x+2)
=>3x-5=3x+6
=>-5=6(vô lý)
=>\(x\in\varnothing\)
h: \(\dfrac{3\left(2x+1\right)}{4}-5-\dfrac{3x+2}{10}=\dfrac{2\left(3x-1\right)}{5}\)
=>\(\dfrac{15\left(2x+1\right)}{20}-\dfrac{100}{20}-\dfrac{2\left(3x+2\right)}{20}=\dfrac{8\left(3x-1\right)}{20}\)
=>\(15\left(2x+1\right)-100-2\left(3x+2\right)=8\left(3x-1\right)\)
=>30x+15-100-6x-4=24x-8
=>24x-89=24x-8
=>-89=-8(vô lý)
=>\(x\in\varnothing\)
