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December 21, 2014

Homework Help: Algebra

Posted by Tamia on Friday, May 18, 2007 at 10:38am.

Please help to find x, y

1. 8x-y=17
6x+y=11

2. 5x-2y=17
2x+3y=3




Question no.1

8x-y=17
6x+y=11 (adding the equation)
__________ (-y and +y will be 0)
14x =28
Taking variables to one side
x=28
__
14
14*2=28
therefore x=2
substitute this value of x in equation 2
6x+y=11
6*2+y=11
12+y=11
y=11-12
y=-1
(x=2)and (y=-1) is the solution of the given equation.





Instead of miley's suggestion, do the following:

Take the value of y in the first formula and substitute it for y in the second formula. Solve the second formula for x.

8x-y=17

-y=17-8x

y=8x-17 (Value of y)

Once x is found, solve for y in the second formula. Check by inserting both values into the first formula.

I hope this helps much more. Thanks for asking.

Question no 2
5x-2y=17 eq 1
2x+3y=3 eq 2
multiply eq 1 by 3
3*5x-3*2y=3*17
15x-6y=51 eq 3
Now multiply eq 2 by 2
2*2x+2*3y=2*3
4x+6y=6 eq 4
15x-6y=51
__________
19x =57 (adding both the equations)
x=57
___
19
x=3
substitute this value of x in eq 2
2x+3y=3
2*3+3y=3
6+3y=3
3y=3-6
3y=-3
y=-1
(x=3) and (y=-1) is the solution of the given equation.


x and the co-effecient cannot be subtracted so the substitution by adding is better

hey tamia can i know by which method are you solving the equation ?

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