Toán Lớp 6: a. |x+3/4|= 1/2 b.|x-6|=8 c.|x+|21-1|=4 d.10-|4-3x|=7

Question

Toán Lớp 6:  a. |x+3/4|= 1/2 b.|x-6|=8 c.|x+|21-1|=4 d.10-|4-3x|=7

truonganhthi · Answer

Giải đáp:   $  $   a,   |x + 3/4| = 1/2   -> x +3/4 = 1/2 hoặc x + 3/4=  (-1)/2   ->x=1/2-3/4 hoặc x=(-1)/2- 3/4   -> x = 2/4 - 3/4 hoặc x= (-2)/4 - 3/4   ->x=(-1)/4 hoặc x=(-5)/4   Vậy x=(-1)/4 hoặc x=(-5)/4   $  $   b,   |x-6| = 8   ->x-6=8 hoặc x-6=-8   ->x=8+6 hoặc x=-8+6   ->x=14 hoặc x=-2   Vậy x=14 hoặc x=-2   $  $   c,   |x + |21-1| | =4   -> |x + |20| | =4   -> |x+20|=4   ->x+20=4 hoặc x+20=-4   ->x=4-20 hoặc x=-4-20   ->x=-16 hoặc x=-24   Vậy x=-16 hoặc x=-24   $  $   d,   10 - |4-3x|=7   -> |4-3x|=10-7   -> |4-3x|=3   -> 4-3x=3 hoặc 4-3x=-3   ->3x=4-3 hoặc 3x=4-(-3)   ->3x=1 hoặc 3x=7   ->x=1&divide;3 hoặc x=7&divide;3   ->x=1/3 hoặc x=7/3   Vậy x=1/3 hoặc x=7/3

tuminh25 · Answer

~rai~        (a) left|x+ dfrac{3}{4} right|= dfrac{1}{2}   Rightarrow  left[ begin{array}{I}x+ dfrac{3}{4}= dfrac{1}{2}  x+ dfrac{3}{4}=- dfrac{1}{2} end{array} right.   Rightarrow  left[ begin{array}{I}x= dfrac{1}{2}- dfrac{3}{4}  x=- dfrac{1}{2}- dfrac{3}{4} end{array} right.   Rightarrow  left[ begin{array}{I}x=- dfrac{1}{4}  x=- dfrac{5}{4}. end{array} right.   text{Vậy x} in left {- dfrac{1}{4};- dfrac{5}{4} right }.  b)|x-6|=8   Rightarrow  left[ begin{array}{I}x-6=8  x-6=-8 end{array} right.   Rightarrow  left[ begin{array}{I}x=8+6  x=-8+6 end{array} right.   Leftrightarrow  left[ begin{array}{I}x=14  x=-2. end{array} right.   text{Vậy x} in {-2;14 }.  c)|x+|21-1||=4   Rightarrow |x+|20||=4   Rightarrow |x+20|=4   Rightarrow  left[ begin{array}{I}x+20=4  x+20=-4. end{array} right.   Rightarrow  left[ begin{array}{I}x=4-20  x=-4-20 end{array} right.   Rightarrow  left[ begin{array}{I}x=-16  x=-24. end{array} right.   text{Vậy x} in {-24;-16 }.  d)10-|4-3x|=7   Rightarrow |4-3x|=10-7   Rightarrow |4-3x|=3   Rightarrow  left[ begin{array}{I}4-3x=3  4-3x=-3 end{array} right.   Rightarrow  left[ begin{array}{I}3x=4-3  3x=4-(-3) end{array} right.   Rightarrow  left[ begin{array}{I}3x=1  3x=7 end{array} right.   Rightarrow  left[ begin{array}{I}x=1:3  x=7:3 end{array} right.   Leftrightarrow  left[ begin{array}{I}x= dfrac{1}{3}  x= dfrac{7}{3}. end{array} right.   text{vậy x} in left { dfrac{1}{3}; dfrac{7}{3} right }. )