Упр.992 ГДЗ Мерзляк Полонский 6 класс (Математика)

1) -2,8 + x + 5,36 + (-7,2) + у + (-7,36), если х = -13, у = 54;
2) m + (-2*4/9) + 8*13/24 + n + (-3*2/9) + (-4*5/24), если m=-3*5/6, n=-2*11/12.

1) При $$x=-13$$, $$y=54$$:

$$ -2{,}8+x+5{,}36+(-7{,}2)+y+(-7{,}36) $$
$$ =(-2{,}8+5{,}36)+(-7{,}2-7{,}36)+x+y $$
$$ =2{,}56-14{,}56+x+y $$
$$ =-12+x+y $$
$$ =-12-13+54 $$
$$ =29 $$

2) При $$m=-3\frac{5}{6}$$, $$n=-2\frac{11}{12}$$:

$$ m+\left(-2\frac{4}{9}\right)+8\frac{13}{24}+n+\left(-3\frac{2}{9}\right)+\left(-4\frac{5}{24}\right) $$
$$ =(m+n)+\left(-2\frac{4}{9}-3\frac{2}{9}\right)+\left(8\frac{13}{24}-4\frac{5}{24}\right) $$
$$ =m+n-5\frac{6}{9}+4\frac{8}{24} $$
$$ =m+n-5\frac{2}{3}+4\frac{1}{3} $$
$$ =m+n-1\frac{1}{3} $$
$$ =-3\frac{5}{6}-2\frac{11}{12}-1\frac{1}{3} $$
$$ =-\left(3\frac{5}{6}+2\frac{11}{12}+1\frac{1}{3}\right) $$
$$ =-\left(5\frac{12}{12}+1\frac{4}{12}\right) $$
$$ =-6\frac{4}{12} =-6\frac{1}{3} $$

Ответ

1) $$29$$; 2) $$-6\frac{1}{3}$$.