Toán Lớp 7: 1) 1/2x 4/5=14/24x-3/2 2) -2|1/2x-1/3|+3/2=1/4 3) (x-3 /7)^2 = 4 4) (x-2 /3)/1 /3 + 5 /6 = 9 5 /6 5) (x-3/4)(x+2/5)=0 mn giúp mì

Question

Toán Lớp 7:  1)  1/2x 4/5=14/24x-3/2  2)  -2|1/2x-1/3|+3/2=1/4 3)  (x-3 /7)^2 = 4 4)  (x-2 /3)/1 /3 + 5 /6 = 9  5 /6 5)  (x-3/4)(x+2/5)=0 mn giúp mình với ạ

minhtuquynh · Answer

$1$) 1/{2x} + 4/5 = 14/{24x} - 3/2   &hArr; 1/{2x} + 4/5 = 7/{12x} - 3/2   &hArr; 7/{12x} - 1/{2x} = 4/5 + 3/2   &hArr; {7-6}/{12x} = 4/5 + 3/2   &hArr; 1/{12x} = {23}/{10}   &rArr; 276x = 10   &hArr; x = {10}/{276}=5/{138}      Vậy x=5/{138}.   $2$) -2|1/{2x} - 1/3| + 3/2 = 1/4   &hArr; -2|1/{2x} - 1/3| = -5/4   &hArr; |1/{2x} - 1/3| = 5/8   &rArr;  ( left[  begin{array}{l} dfrac{1}{2x}- dfrac{1}{3}= dfrac{5}{8}   dfrac{1}{2x}- dfrac{1}{3}=- dfrac{5}{8} end{array}  right. )    $&hArr;$  ( left[  begin{array}{l} dfrac{1}{2x} =  dfrac{23}{24}   dfrac{1}{2x}= dfrac{-7}{24} end{array}  right. )    $&hArr;$  ( left[  begin{array}{l}x= dfrac{12}{23}  x= dfrac{-12}{7} end{array}  right. )        Vậy $x$ $&isin;$ {{-12}/7;{12}/{23}}   $3$) (x-3/7)^2 = 4   &rArr;  ( left[  begin{array}{l}x- dfrac{3}{7}=2  x- dfrac{3}{7}=-2 end{array}  right. )   $&rArr;$  ( left[  begin{array}{l}x= dfrac{17}{7}  x= dfrac{-11}{7} end{array}  right. )     Vậy $x$ $&isin;$ {-{11}/7;{17}/7}.   $4$) {(x-2/3)}/{1/3} + 5/6 = 9 5/6    &hArr;{(x-2/3)}/{1/3} = 9     &hArr; x - 2/3 = 3     &hArr; x = {11}/3        Vậy x={11}/3.     $5$) (x-3/4)(x+2/5)=0     &rArr;  ( left[  begin{array}{l}x= dfrac{3}{4}  x= dfrac{-2}{5} end{array}  right. )        Vậy $x$ $&isin;$ {-2/5;3/4}.

thaolanphuobg · Answer

Giải đáp:       Lời giải và giải thích chi tiết:   1.   1/2x+4/5=14/24x-3/2   =>1/2x+23/10=14/24x   =>23/10=x.(14/24-1/2)   =>23/10=x*1/12   =>x=138/5   Vậy x=138/5.   2.   $-2. left| dfrac{1}{2}x- dfrac{1}{3} right|+ dfrac{3}{2}= dfrac{1}{4}   Rightarrow-2. left| dfrac{1}{2}x- dfrac13 right|= dfrac{-5}{4}   Rightarrow left| dfrac12x- dfrac13 right|= dfrac{5}{8}$   =>1/2x-1/3=5/8 hoặc 1/2x-1/3=(-5)/8   =>1/2x=23/24                  1/2x=(-7)/24   =>x=23/12                     1/2x=(-7)/12   Vậy x in{23/12;(-7)/12}.   3.   (x-3/7)^2=(+-2)^2   =>x-3/7=2 hoặc $x- dfrac37=-2$   =>x=17/7               x=(-11)/7   Vậy x in{17/7;(-11)/7}.   4.    (x-2/3):1/3+5/6=9 5/6   =>(x-2/3):1/3=9   =>x-2/3=3   =>x=11/3   Vậy x=11/3.   5.   (x-3/4).(x+2/5)=0   =>x-3/4=0 hoặc x+2/5=0   =>x=3/4                   x=(-2)/5   Vậy x in{3/4;(-2)/5}.