a)3/4-1/4(x+1)=2/5 b)40%x-1/2/5x=0,75 c)x-2/7=7/x-2
1/4(x+1) = 3/4-2/5 2/5x-7/5x=3/4 ⇒(x-2)(x-2)=(-7).(-7)
1/4(x+1) = 15/20-8/20 (2/5+7/5)x=3/4 ⇒(x-2)²=49
1/4(x+1)=7/20 9/5x=3/4 ⇒x-2=7 hoặc x-2=-7
x+1=7/20:1/4 x=3/4:9/5 ⇒x=9 hoặc x=-5
x+1=7/20.4 x=3/4.5/9
x+1=7/5 x=5/12
x=7/5-1
x=2/5
d)l3x-2/5l-4/7=1/3/7
l3x-2/5l-4/7=10/7
l3x-2/5l = 10/7+4/7
l3x-2/5l = 2
⇒3x-2/5=2 hoặc 3x-2/5=-2
⇒3x=2+2/5 hoặc 3x=-2+2/5
⇒3x=12/5 hoặc 3x=-8/5
⇒x=12/5:3 hoặc x=-8/5:3
⇒x=4/5 hoặc x=-8/15
