Toán Lớp 7: Bài 1: a,2x/3=4/5 b, 4:5x = 3:7 c.12/x = x/3

Question

Toán Lớp 7:  Bài 1: a,2x/3=4/5 b, 4:5x = 3:7 c.12/x = x/3

trucoanh55 · Answer

B&agrave;i 1:   a, frac{2x}{3} = 4/5     2x &middot; 5 = 3 &middot; 4     2x &middot; 5 = 12     2x = 12 : 5     2x = 12/5     x = 12/5 : 2     x = 12/5 &middot; 1/2     x = 12/10     x = 6/5   Vậy x = 6/5   b, 4 : 5x = 3 : 7     frac{4}{5x} = 3/7     5x &middot; 3 = 4 &middot; 7      5x &middot; 3 = 28     5x = 28 : 3     5x = 28/3     x = 28/3 : 5     x = 28/3 &middot; 1/5     x = 28/15   Vậy x = 28/15   c, 12/x = x/3     x &middot; x = 12 &middot; 3     x^2 = 36     x^2 = 6^2         x = &plusmn; 6   Vậy x = 6 v&agrave; x = -6

diemmyhoa · Answer

~ Bạn tham khảo ~   a) (2x)/3 = 4/5   => (2x)5 = 3.4   => (2x)5 = 12   => 2x = 12 : 5   => 2x = 12/5   => x = 12/5 : 2   => x = 1,2   Vậy  x = 1,2   b) 4:5x = 3:7   4/(5x) = 3/7   => 4.7 = (5x)3   => 28 = (5x)3   => 5x = 28  :3   => 5x = 28/3   => x = 28/3 : 5   => x = 28/15   Vậy  x = 28/15   c) 12/x = x/3   => 12.3 = x.x   => 36 = x^2   => x = (+-6)^2   Vậy  x in { -6 ;6}   $#Vịt v&agrave;ng$