# Maths

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

• Maths -

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 -

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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