SOLUTION: find two factors of 28 with the sum of 11?

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Question 106125: find two factors of 28 with the sum of 11?
Answer by alvinjohnburgos(11) About Me  (Show Source):
You can put this solution on YOUR website!
If we use x and y as variables for the factors:
eq1xy+=+28
eq2x+%2B+y+=+11
isolate y in eq2:
y+=+11+-+x
Substitute (11-x) for y in eq1:
%28x%29%2811-x%29+=+28
11x+-+x%5E2+=+28
-x%5E2+%2B+11x+-+28+=+0+
x%5E2+-+11x+%2B+28+=+0+
Quadratic formula:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x+=+%2811+%2B-+sqrt%28%28-11%29%5E2+-+4%2A1%2A28%29%29%2F%282%2A1%29
Simplifying:
x+=+7+or+4
Substitute values in eq2:
7+%2B+y+=+11
y+=+4
4+%2B+y+=+11
y+=+7
So, the two factors are 7 and 4.