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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: a) (4/5)^x=64/125 b) |-7/9+x|-5/6=1/18 c) (-1 2/3-x).(2x+3/7)=0

Toán Lớp 7: a) (4/5)^x=64/125
b) |-7/9+x|-5/6=1/18
c) (-1 2/3-x).(2x+3/7)=0

Comments ( 1 )

  1. Giải đáp:
    a) ta có x=3 . vì $\frac{4}{5}$ ^3 = $\frac{64}{125}$ 
    b) |-$\frac{7}{9}$ + x | – $\frac{5}{6}$  = $\frac{1}{18}$ 
        |-$\frac{7}{9}$ + x |                          =$\frac{1}{18}$ + $\frac{5}{6}$ 
        |-$\frac{7}{9}$ + x |                           =$\frac{1}{18}$ +$\frac{15}{18}$ 
        |-$\frac{7}{9}$ + x |                          = $\frac{16}{18}$ =$\frac{8}{9}$ 
                              $\left \{ {{x=15/9} \atop {x=-1/9}} \right.$ 
    c) (-1$\frac{2}{3}$ -x). (2x+$\frac{3}{7}$ )=0
    $\left \{ {{-1+2/3-x=0}} \atop {2x+3/7=0}} \right.$  ⇒ $\left \{ {{5/3-x=0} \atop {2x=-3/7}} \right.$ ⇒ $\left \{ {{x=-5/3} \atop {x=-3/14}} \right.$ 
    5sao và ctlhn

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222-9+11+12:2*14+14 = ? ( )

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