Question

вывести в общий знаменатель
2х + 1 3 7х
____ - __ = __
2 4 8

Answer 1

$2x+ frac{1}{2} - frac{3}{4} = frac{7x}{8} \ \ 2x+ frac{1*4}{2*4} - frac{3*2}{4*2} = frac{7x}{8} \ \ 2x + frac{4-6}{8} = frac{7x}{8} \ \ 2x- frac{2}{8} = frac{7x}{8}$ 
8*2x - 2 = 7x
16x-7x=2
9x=2
x= $frac{2}{9}$
Проверим:

$2* frac{2}{9} + frac{1}{2} - frac{3}{4} = frac{7* frac{2}{9} }{8} \ \ frac{4*4}{4*9} + frac{18*1}{18*2} - frac{3*9}{4*9} = frac{14}{9} * frac{1}{8} \ \ frac{16+18-27}{36} = frac{7*1}{9*4} \ \ frac{7}{36} = frac{7}{36}$