Math Is Fun Forum

amylt77

Guest

Help

I am terrible at math and I need major help:

The problems are:

Solve each system by the substitution method

x = -3y +2
7y = 3x

and the second is

Solve each system by sustitution or addition, whichever is easier

x + y = 3
7x - y =29

This may be easy for some but I have NO clue so if you can help I would really appreciate it...Thanks

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 51,348

Re: Help

amylt77,
For the first set of equations, given:
x = -3y +2
7y = 3x

Multiply the first equation by 3, you get
3x = -9y + 6
But from the second equation, you know that 7y=3x. Hence, substitute 7y in place of 3x. You get
7y=-9y+6 or 16y=6 or y=6/16 or 3/8.
Substitute this value of y in the second equation,
21/8 = 3x or x = 7/8.

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The second system of equations is relatively easier to solve:-

Solve each system by sustitution or addition, whichever is easier

x + y = 3
7x - y =29

Adding the two equations, you get 8x=32 as the +y and -y get cancelled.
That is x=4.
From the first equation, 4+y=3, or y = 3-4 = -1.

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amylt

Guest

Re: Help

THANK YOU!!!!!! You have saved me