Câu 2:
a) `-4/7 x + 1/3 = 7/3`
`=> -4/7 x = 7/3 - 1/3`
`=> -4/7 x= 2`
`=> x= 2 : (-4/7)`
`=> x= 2. (-7/4)`
`=> x = -7/2`
Vậy `x= -7/2`
b) `| 3/5 sqrt x - 1/20| - 3/4 = 1/5`
`=> |3/5 sqrt x - 1/20| = 1/5 + 3/4`
`=> |3/5 sqrt x - 1/20| = 19/20`
+) `3/5 sqrt x - 1/20 = 19/20`
`=> 3/5 sqrt x = 19/20 + 1/20`
`=> 3/5 sqrt x = 1`
`=> sqrt x = 1 : 3/5`
`=> sqrt x=1 . 5/3`
`=> sqrt x = 5/3`
`=> x = (5/3)^2`
`=> x= 25/9`
+) `3/5 sqrt x - 1/20 = -19/20`
`=> 3/5 sqrt x= -19/20 + 1/20`
`=> 3/5 sqrt x=-9/10`
`=> sqrt x= -9/10 : 3/5`
`=> sqrt x = -9/10 . 5/3`
`=> sqrt x = -3/2`
`=>` không tìm được `x` vì `sqrt x ge 0`
Vậy `x= 25/9`
c) `2^x + 2^(x+4) = 544`
`=> 2^x + 2^x . 2^4 = 544`
`=> 2^x ( 1 + 2^4) = 544`
`=> 2^x . 17 = 544`
`=> 2^x = 544:17`
`=> 2^x = 32`
`=> 2^x = 2^5`
`=> x=5`
Vậy `x=5`
d) `(10 - 2x)/5= 27/(5-x)`
`=> (5-x)(10-2x) = 27.5`
`=> (5-x)2(5 -x) = 135`
`=> (5-x)^2 = 135 :2`
`=> (5-x)^2= ((3sqrt(30)) / sqrt2)^2` hoặc ` (5-x)^2= ((-3sqrt(30)) / sqrt2)^2`
+) `(5-x)^2= ((3sqrt(30)) / sqrt2)^2`
`=> 5-x = (3sqrt(30)) / sqrt2`
`=> x= 5- (3sqrt(30)) / sqrt2`
+) ` (5-x)^2= ((-3sqrt(30)) / sqrt2)^2`
`=> 5-x = (-3sqrt(30)) / sqrt2`
`=> x = 5 + (3sqrt(30)) / sqrt2`
Vậy `x = 5 + (3sqrt(30)) / sqrt2` hoặc `x= 5- (3sqrt(30)) / sqrt2`
