Toán Lớp 7: Tìm x a,x/52=-14/39 b|3x-1|=1/3x+2|

Question

Toán Lớp 7:  Tìm x  a,x/52=-14/39 b|3x-1|=1/3x+2|

phuongthuydung · Answer

Answer    a,   x/52 = {-14}/39   $ Rightarrow$ 39x = -14 . 52   $ Rightarrow$ 39x = -728   $ Rightarrow$ x = -728 : 39   $ Rightarrow$ x = -56/3   $ text{Vậy}$ x = -56/3   ____________________   b, |3x - 1| = |1/3x + 2|   $ text{TH1:}$   3x - 1 = 1/3x + 2   $ Rightarrow$ 3x - 1/3x = 2 + 1   $ Rightarrow$ 8/3x = 3   $ Rightarrow$ x = 3 : 8/3   $ Rightarrow$ x = 9/8   $ text{TH2:}$   3x - 1 = -(1/3x + 2)   $ Rightarrow$ 3x - 1 = - 1/3x - 2   $ Rightarrow$ 3x + 1/3x = -2 + 1   $ Rightarrow$ 10/3x = -1   $ Rightarrow$ x = -1 : 10/3   $ Rightarrow$ x = -3/10   $ text{Vậy}$ x  in {9/8 ; -3/10}

tuyetnhungthu · Answer

a) x/52=-14/39   &hArr; x.39=52.(-14)   &hArr; x.39=-728   &hArr; x=-728 : 39   &rArr; x=-56/3   $ text{Vậy ......}$   b) |3x-1|=|1/3x+2|   &hArr; $ bigg|3x - 1 bigg| = bigg | dfrac{1}{3}x + 2 bigg|$   &hArr; $ bigg|3x - 1 bigg| = &plusmn;  dfrac{1}{3} + 2$   &hArr;  ( left[  begin{array}{l}3x-1= dfrac{1}{3}x+2  3x-1=- dfrac{1}{3}x+2 end{array}  right. )   &hArr;  ( left[  begin{array}{l}3x- dfrac{1}{3}x=1+2  3x+ dfrac{1}{3}x=1+2 end{array}  right. )   &hArr;  ( left[  begin{array}{l} dfrac{8}{3}x=3   dfrac{10}{3}x=3 end{array}  right. )   &rArr;  ( left[  begin{array}{l}x=1.125  x=0.9 end{array}  right. )   $ text{Vậy ......}$   @Sano    $ text{Ch&uacute;c bn hok tốt}$