Question

Решите по действиям:
1)(-3,9×2,8+26,6)×(-3,2)-2,1
2)-5/9×0,87+(-5/9)×1,83
__________
Решите уравнение:
1)-0,25Х+0,8=1,3
2)(5-Х)(2Х+8)=0
3)-1,6/Х-2=2,8/4,2

Answer 1

▪1)
$( - 3.9 times 2.8 + 26.6) times ( - 3.2) - 2.1 = - 52.276\ 1) : : : - 3.9 times 2.8 = - 10.92 \ 2) : : : - 10.92 + 26.6 = 15.68 \ 3) : : : 15.68 times ( - 3.2) = - 50.176 \ 4) : : : - 50.176 - 2.1 = - 52.276$
▪2)
$- frac{5}{9} times 0.87 + ( - frac{5}{9} ) times 1.83 = - frac{5}{9} times (0.87 + 1.83) = - frac{5}{9} times 2.7 = - frac{5 times 27}{9 times 10} = - frac{3}{2} = - 1 frac{1}{2} = - 1.5$
уравнения
▪1)
$- 0.25x + 0.8 = 1.3 \ - 0.25x = 1.3 - 0.8 \ - 0.25x = 0.5 \ x = 0.5 div ( - 0.25) = frac{5}{10} div ( - frac{25}{100} ) = frac{1}{2} div ( - frac{1}{4} ) = - frac{4}{2} = - 2 \ x = - 2$
▪2)
$(5 - x)(2x + 8) = 0 \ 5 - x = 0 \ x1 = 5 \ - - - - - - - - \ 2x + 8 = 0 \ 2x = - 8 \ x2 = - frac{8}{2} \ x2 = - 4 \ - - - - - - - -$
▪3)
$frac{ - 1.6}{x - 2} = frac{2.8}{4.2} \ 2.8x - 5.6 = - 6.72 \ 2.8x = - 6.72 + 5.6 \ 2.8x = - 1.12 \ x = - 1.12 div 2.8 = - frac{112}{100} times frac{10}{28} = - frac{4}{10} \ x = - 0.4$