Basic Math Problem

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May 16th 2009, 11:57 AM
Aslam Anjum

Basic Math Problem

I need help on a question the questions says

by eliminating Y, find the solution to the Simulataneous Eqautions.

X(squared)+Y(squared)=25
Y=X-7

Thanks in Advance,
Aslam
May 16th 2009, 11:59 AM
artvandalay11

Plug x-7 in for y in the first equation so $x^2+(x-7)^2=25$
May 16th 2009, 12:00 PM
e^(i*pi)

Quote:

Originally Posted by Aslam Anjum

I need help on a question the questions says

by eliminating Y, find the solution to the Simulataneous Eqautions.

X(squared)+Y(squared)=25
Y=X-7

Thanks in Advance,
Aslam

$x^2+y^2 = 25$

As you've stated y=x-7 so we can sub that in for where we see 'y' in the first equation.

$x^2 + (x-7)^2 = 25 \: , \: x^2 + x^2 - 14x + 49 = 25$

$2x^2 - 14x + 24 = 0$
May 16th 2009, 12:08 PM
Aslam Anjum

Thanks for that but I think this is a quadratic as there is space to put two sets of values for X and Y.

can you please work it out and tell what the answers are so i can check to see if I'm gettting the right answers

Thanks again,

Aslam
May 16th 2009, 12:16 PM
artvandalay11

You can tell us what you get for answers and we'll tell you if you are right. This forum is to help people not to do it for you
May 16th 2009, 12:22 PM
e^(i*pi)

Quote:

Originally Posted by Aslam Anjum

Thanks for that but I think this is a quadratic as there is space to put two sets of values for X and Y.

can you please work it out and tell what the answers are so i can check to see if I'm gettting the right answers

Thanks again,

Aslam

Well you can solve that equation to find x and from there find y:

$2x^2 - 14x + 24 = 0$

Divide by 2: $x^2 - 7x+12 = 0$

I can see that this factorises to $(x-4)(x-3) = 0$

therefore either x-4=0 or x-3=0 and therefore x = 4 or x=3.

We then put these back into y = x-7

y = 4-7 = -3 or y = 3-7 = -3.

Our solutions are therefore x=4, y=-3 or x=3, y=-4. There are two pairs of answers for this
May 16th 2009, 12:48 PM
Aslam Anjum

thanks for that i didnt get anything close to that I started using the other eqaution i cant tell which equation to use when i see the questions.

thanks for the help,

Aslam