Toán Lớp 7: |7x+1|-|5x+6|=0 |3/2x+1/2|=|4x-1| |5/4x-7/2|-|5/8x+3/5|=0

Question

Toán Lớp 7:  |7x+1|-|5x+6|=0 |3/2x+1/2|=|4x-1| |5/4x-7/2|-|5/8x+3/5|=0

diemmyhoa · Answer

Giải đáp:     a. S={ frac{5}{2};- frac{7}{12}}   b. S={ frac{3}{5}; frac{1}{11}}   c. S={ frac{164}{25}; frac{116}{75}}     Lời giải và giải thích chi tiết:     a. |7x+1|-|5x+6|=0   &harr;|7x+1|=|5x+6|   &harr; ( left[  begin{array}{l}7x+1=5x+6  7x+1=-5x-6 end{array}  right. )    &harr; ( left[  begin{array}{l}2x=5  12x=-7 end{array}  right. )    &harr; ( left[  begin{array}{l}x= dfrac{5}{2}  x=- dfrac{7}{12} end{array}  right. )    Vậy: S={ frac{5}{2};- frac{7}{12}}   b. | frac{3}{2}x+ frac{1}{2}|=|4x-1|   &harr; ( left[  begin{array}{l} dfrac{3}{2}x+ dfrac{1}{2}=4x-1   dfrac{3}{2}x+ dfrac{1}{2}=-4x+1 end{array}  right. )    &harr; ( left[  begin{array}{l}5x=3  11x=1 end{array}  right. )    &harr; ( left[  begin{array}{l}x= dfrac{3}{5}  x= dfrac{1}{11} end{array}  right. )    Vậy: S={ frac{3}{5}; frac{1}{11}}   c. | frac{5}{4}x- frac{7}{2}|-| frac{5}{8}x+ frac{3}{5}|=0   &harr;| frac{5}{4}x- frac{7}{2}=| frac{5}{8}x+ frac{3}{5}|   &harr; ( left[  begin{array}{l} dfrac{5}{4}x- dfrac{7}{2}= dfrac{5}{8}x+ dfrac{3}{5}   dfrac{5}{4}x- dfrac{7}{2}=- dfrac{5}{8}x- dfrac{3}{5} end{array}  right. )    &harr; ( left[  begin{array}{l}5x= dfrac{164}{5}  15x= dfrac{116}{5} end{array}  right. )    &harr; ( left[  begin{array}{l}x= dfrac{164}{25}  x= dfrac{116}{75} end{array}  right. )    Vậy: S={ frac{164}{25}; frac{116}{75}}