Posted by **Smangele Phakathi** on Friday, September 20, 2013 at 3:23am.

Can you pliz help me solve the following simultaneous equation 3x-y=2 and 3y+9x=4

- Maths -
**MS**, Friday, September 20, 2013 at 4:22am
3x-y=2 Multiplt it by 3

9x-3y=6 Add to it the other eq.

9x+3y=4 You get 18x=10 or x=5/9

Substitute in any eq.

3*5/9-y=2 or y=15/9-2=5/3 -2

or y=(5-6)/2=-1/6.

Check: 3*5/9-(-1/6)=2 or 5/3+1/6=2

or (10+2)/6=2 ok.

9*5/9-3*1/3=4 or 5-1=4 ok.

- check answer - Maths -
**Reiny**, Friday, September 20, 2013 at 7:35am
or ... using substitution

from the 1st: y = 3x-2

sub into the 2nd

3(3x-2) + 9x = 4

9x - 6 + 9x = 4

18x = 10

x = 5/9

back into the 1st:

y = 3(5/9) - 2

= 5/3 - 2

= -1/3

in original:

1st equation:

LS = 3(5/9) - (-1/3) = 6/3 = 2 = RS

2nd equation:

LS= 3(-1/3) + 9(5/9) = -1 + 5 = 4 = RS

So x = 5/9 and y = -1/3

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