Question

Решите уравнения: 

а) 7(2 + у) - 3у = 5у - 6

б) 4х - 2(3 + х) = 9 - х

г) -3(5а - 1) +4а = 2а + 7(5 - 3а) 

Answer 1

a) 7(2+y)-3y=5y-6;

14+7y-3y=5y-6;

14+4y=5y-6;

4y-5y=-6-14;

-y=-20;

y=20!

 

б) 4x-2(3+x)=9-x;

4x-6-2x=9-x;

2x-6=9-x;

2x+x=9+6;

3x=15;

x=5!

 

г) -3(5a-1)+4a=2a+7(5-3a);

-15a+3+4a=2a+35-21a;

-11a+3=-19a+35;

-11a+19a=35-3;

8a=32;

a=32/8;

a=4!

 

Answer 2

а) $7(2+y)-3y=5y-6$

 

$14+7y-3y=5y-6$

 

$14+4y=5y-6$

 

$5y-4y=14+6$

 

$y=20$

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$7(2+20)-3cdot20=5cdot20-6$ (это проверка)

 

$7cdot22-60=100-6$

 

$154-60=94$

 

$94=94$

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б) $4x-2(3+x)=9-x$

 

$4x-6-2x=9-x$

 

$2x-6=9-x$

 

$2x+x=9+6$

 

$3x=15$

 

$x=15:3$

 

$x=5$

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$4cdot5-2(3+5)=9-5$

 

$20-2cdot8=4$

 

$20-16=4$

 

$4=4$

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г) $-3(5a-1)+4a=2a+7(5-3a)$

 

$-15a+3+4a=2a+35-21a$

 

$-11a+3=35-19a$

 

$19a-11a=35-3$

 

$8a=32$

 

$8a=32$

 

$a=32:8$

 

$a=4$

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$-3(5cdot4-1)+4cdot4=2cdot4+7(5-3cdot4)$

 

$-3(20-1)+16=8+7(5-12)$

 

$-3cdot19+16=8+7cdot(-7)$

 

$-57+16=8-49$

 

$-41=-41$