Saturday, June 16, 2012

If x^2 + y^2 = 29 and x+ y = 7 Then find x and y.

Given the equations:


x^2 +
y^2 = 29..............(1)


x+ y =
7.......................(2)


We have a system of two
equations and two variables. Then, we can use the substitution or the elimination method
to solve.


Let us use the substitution method to
solve.


We will re-write equation
(2).


x+ y = 7


==> y = 7
- x


Now we will substitute in
(1).


x^2 + y^2 = 29


==>
x^2 + ( 7-x)^2 = 29


==> x^2 + 49 - 14x + x^2 =
29


==> 2x^2 - 14x + 49 - 29 =
0


==> 2x^2 - 14x + 20 =
0


Now we will divide by
2:


==> x^2 - 7x + 10 =
0


==> ( x - 2) ( x- 5) =
0


==> x1 = 2  ==> y1= 7-2 =
5


==> x2= 5 ==> y2= 7-5 =
2


Then the answer is the
pairs:


( 2, 5) OR ( 5, 2)

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