Đáp án:
`a,`
`1 3/4 x - 5 = 3 1/3`
`-> 7/4x - 5 = 10/3`
`-> 7/4x = 10/3 + 5`
`-> 7/4x = 25/3`
`-> x= 25/3 ÷ 7/4`
`-> x = 100/21`
Vậy `x = 100/21`
`b,`
`2/3x + 1/4 = 7/12`
`-> 2/3x = 7/12 - 1/4`
`-> 2/3x = 1/3`
`-> x = 1/3 ÷ 2/3`
`-> x = 1/2`
Vậy `x = 1/2`
`c,`
`1/3 + 2/5 (x + 1) = 1`
`-> 2/5 (x + 1) = 1 - 1/3`
`-> 2/5 (x + 1) = 2/3`
`-> x + 1 = 2/3 ÷ 2/5`
`-> x + 1 =5/3`
`-> x = 5/3 - 1`
`-> x = 2/3`
Vậy `x = 2/3`
`d,`
`1/4 + 1/3 ÷ 3x = -5`
`-> 1/3 ÷ 3x = -5 - 1/4`
`-> 1/3 ÷ 3x = (-21)/4`
`-> 3x = 1/3 ÷ (-21)/4`
`-> 3x = (-4)/63`
`-> x = (-4)/63 ÷ 3`
`-> x = (-4)/189`
Vậy `x = (-4)/189`
`e,`
`2x^2 - 72 = 0`
`-> 2x^2 = 0 + 72`
`-> 2x^2 = 72`
`-> x^2 = 72 ÷ 2`
`-> x^2 = 36`
`->` \(\left[ \begin{array}{l}x^2=6^2\\x^2=(-6)^2\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=6\\x=-6\end{array} \right.\)
Vậy `x=6` hoặc `x=-6`
`f,`
`(3/5x - 0,75) ÷ 3/7 = 2 4/5`
`-> (3/5x - 0,75) ÷ 3/7 = 14/5`
`-> 3/5x - 0,75 = 14/5 × 3/7`
`-> 3/5x - 0,75 = 6/5`
`-> 3/5x = 6/5 + 0,75`
`-> 3/5x = 39/20`
`-> x = 39/20 ÷ 3/5`
`-> x = 13/4`
Vậy `x = 13/4`
`g,`
`2x + 3/10 = 1 5/6 × 6/11`
`-> 2x + 3/10 = 11/6 × 6/11`
`-> 2x + 3/10 = 1`
`-> 2x = 1 - 3/10`
`-> 2x = 7/10`
`-> x = 7/10 ÷ 2`
`-> x = 7/20`
Vậy `x = 7/20`
`h,`
`1/4 ÷ (x - 7 1/3) = -1,5`
`-> 1/4 ÷ (x - 22/3) = -1,5`
`-> x - 22/3 = 1/4 ÷ (-1,5)`
`-> x - 22/3 = (-1)/6`
`-> x = (-1)/6 + 22/3`
`-> x = 43/6`
Vậy `x = 43/6`
`i,`
`|x - 3| = 6`
`->` \(\left[ \begin{array}{l}x-3=6\\x-3=-6\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=9\\x=-3\end{array} \right.\)
Vậy `x=9` hoặc `x = -3`
`k,`
`12 - |x| = 8`
`-> |x| = 12 - 8`
`-> |x| = 4`
`->` \(\left[ \begin{array}{l}x=4\\x=-4\end{array} \right.\)
Vậy `x=4` hoặc `x = -4`
`l,`
`(x - 2/3)^2 = 5/6`
`-> x - 2/3 = \sqrt{5/6}` hoặc `x -2/3 = -\sqrt{5/6}`
`-> x = (4 + \sqrt{30})/6` hoặc `x = (4 - \sqrt{30})/6`
Vậy `x (4 + \sqrt{30})/6` hoặc `x = (4 - \sqrt{30})/6`
`m,`
`(3/4 - x)^3 = -8`
`-> (3/4 - x)^3 = -2^3`
`-> 3/4 - x = -2`
`->x = 3/4 - (-2)`
`-> x = 11/4`
Vậy `x = 11/4`
