Bài `1` :
`A = 2/7 + 3/7 : (-3/2)`
`A = 2/7 + 3/7 . (-2)/3`
`A = 2/7 + (-2)/7`
`A = 0`
`B = -5/17 - 31/33 + (-5)/17 . 2/33 + 2 5/17`
`B = -5/17 . 31/33 + (-5)/17 . 2/33 + 39/17`
`B = -5/17 ( 31/33 + 2/33 ) + 39/17`
`B = -5/17 . 1 + 39/17`
`B = -5/17 + 39/17`
`B = 34/17`
`B = 2`
`C = (0,125)^10 . 8^10`
`C = ( 0,125 . 8 )^10`
`C = 1^10`
`C = 1`
`D = (2^15 . 9^5)/(6^8 . 8^3)`
`D = (2^15 . (3^2)^5)/((2 . 3)^8 . (2^3)^3)`
`D = (2^15 . 3^10)/(2^8 . 3^8 . 2^6)`
`D = (2^15 . 3^10)/(2^14 . 3^8)`
`D = 2 . 3^2`
`D = 2 . 9`
`D = 18`
Bài `2` :
`a, 3/5 . x + 2/3 = 2 2/3`
`3/5 . x + 2/3 = 9/3`
`3/5 . x = 9/3 - 2/3`
`3/5 . x = 7/3`
`x = 7/3 : 3/5`
`x = 7/3 . 5/3`
`x = 35/9`
`b, 5 - | 3x - 1 | = 3`
`| 3x - 1 | = 5 - 3`
`| 3x - 1 | = 2`
`⇒ 3x - 1 = 2` hoặc `3x - 1 = -2`
`⇒ 3x = 3` `3x = -1`
`⇒ x = 1` `x = -1/3`
Vậy `x = 1` hoặc `x = -1/3`
`c, 0,3 . x : 3 1/3 = 6 : 15`
`3/10 . x : 10/3 = 2/5`
`3/10 . x . 10/3 = 2/5`
`x = 2/5`
Vậy `x = 2/5`
`d, 9 . (x-1)^2 - 4/9 : 2/9 = 1/4`
`9 . (x-1)^2 - 4/9 . 9/2 = 1/4`
`9 . (x-1)^2 - 2 = 1/4`
`9 . (x-1)^2 = 1/4 + 2`
`9 . (x-1)^2 = 1/4 + 8/4`
`9 . (x-1)^2 = 9/4`
`(x-1)^2 = 9/4 : 9`
`(x-1)^2 = 9/4 . 1/9`
`(x-1)^2 = 1/4`
`⇒ (x-1)^2 = (1/2)^2`
`⇒ x - 1 = 1/2`
`⇒ x = 1/2 - 1`
`⇒ x = 1/2 - 2/2`
`⇒ x = -1/2`
Vậy `x = -1/2`
`e, ( 3x - 1 )^6 = ( 3x - 1 )^4`
`( 3x - 1 )^6 - ( 3x - 1 )^4 = 0`
`( 3x - 1 )^4 . [ ( 3x - 1 )^2 - 1 ] = 0`
`⇒ 3x - 1 = 0` hoặc `3x - 1 = 1` hoặc `3x - 1 = -1`
`⇒ 3x = 1` `3x = 2` `3x = 0
`⇒ x = 1/3` `x = 2/3` `x = 0`
Vậy `x = 1/3` hoặc `x = 2/3` hoặc `x = 0`
