SOLUTION: 3 times a number is 28 less than the square of that number. Find the positive solution.

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Question 421079: 3 times a number is 28 less than the square of that number. Find the positive solution.
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

3 times a number is 28 less than the square of that number
let a number be x
3x%2B28=x%5E2
x%5E2-3x-28=0

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x+=+%28-%28-3%29+%2B-+sqrt%28+%28-3%29%5E2-4%2A1%2A%28-28%29+%29%29%2F%282%2A1%29+
x+=+%283+%2B-+sqrt%28+9+%2B+112+%29%29%2F2+
x+=+%283+%2B-+sqrt%28++121+%29%29%2F2+
x+=+%283+%2B-+%28++11%29%29%2F2+
positive solution
x+=+%283+%2B++11%29%2F2+
x+=++14%2F2+
x+=++7+
check:
3x%2B28=x%5E2
3%2A7%2B28=7%5E2
21%2B28=49
49=49