Question

очень прошу помочь! даю 25 баллов

Answer 1

2)
$a)2b - a + 4b - 7a+ 7 = \ = 6b - 8a + 7$
б)
$y + 3(x - 2y) = y + 3x - 6y = \ = - 5y + 3x$
в)
$10n - (5n - 3) + (3n - 1) = \ 10n - 5n + 3 +3n - 1 = \ 8n + 2$
3.
а)
$- 8x = 24 \ x = 24 div ( - 8) \ x = - 3$
б)
$3x + 7 = 0 \ 3x = 0 - 7 = - 7 \ x = - 7 div 3 = - frac{7}{3} = - 2 frac{1}{3}$
в)
$13 - 5x - 8 + 2x = 0 \ 5 - 3x = 0 \ 3x = 5 - 0 = 5 \ x = frac{5}{3} = 1 frac{2}{3}$
Г)
$7x + 1 - 6x - 3 = 5\ x - 2 = 5 \ x = 5 + 2 = 7$
$2 frac{1}{3} ( - 0.7 + 6) - 7 frac{2}{3} (3 + 0.7) = \ 2 frac{1}{3} times 5 frac{3}{10} - 7 frac{2}{3} times 3 frac{7}{10} = - 16$
$2 frac{1}{ 3} times 5 frac{3}{10} = frac{7}{3} times frac{53}{10} = frac{371}{30} = 12 frac{11}{30}$
$7 frac{2}{3} times 3 frac{7}{10} = frac{23}{3} times frac{37}{10} = frac{851}{30} = 28 frac{11}{30}$
$12 frac{11}{30} - 28 frac{11}{30} = - 16$

Answer 2

2) в) неверно

Answer 3

№2

а)$2b-a+5b-7a+7=7b-8a+7$

б)$y + 3(x - 2y) = y + 3x -6y = 3x - 5y$

в)$10n-(5n-3)+(3n-1)=10n-5n+3+3n-1=8n+2$

№3

а)$-8x=24\8x=-24\x=-frac{24}{8}=-3$

б)$3x+7=0\3x=-7\x=-frac{7}{3}=-2frac{1}{3}$

в)$13-5x=8-2x\5-3x=0\5=3x\x=frac{5}{3}=1frac{2}{3}$

г)$(7x+1)-(6x+3)=5\7x+1-6x-3=5\x-2=5\x=7$

№4

Пусть первый изготовил a деталей, второй - b.

$left { {{a+b=657} atop {a=b+63}} right.left { {{b+63+b=657} atop {a=b+63}} right.left { {{2b=594} atop {a=b+63}} right.left { {{b=297} atop {a=297+63}} right.left { {{b=297} atop {a=360}} right.$

№5

$2frac{1}{3}(-0.7+6)-7frac{2}{3}(3+0.7)=2frac{1}{3}*5.3-7frac{2}{3}*3.7=frac{7*53}{3*10}-frac{23*37}{3*10}=-frac{371-851}{30}=-frac{480}{30}=-16$

№6

$6(x-1)+3(5-x)=9\6x-6+15-3x=9\9x+9=9\9x=0\x=0$

№7

Пусть карандашей было a, кистей b, линеек c.

$left { {a+b+c=43 atop c=b-7} atop  c=frac{a}{4}} right.left { {a+b+b-7=43 atop c=b-7} atop  a=4c} right. left { {4b-28+2b=50 atop c=b-7} atop  a=4b-28} right. left { {6b=78 atop c=b-7} atop  a=4(b-7)} right. left { {b=13 atop c=b-7} atop  a=4(b-7)} right. left { {b=13 atop c=6} atop  a=24} right.$

Answer 4

2a) 2b-a+4b-7a+7=6b-8a+7