SOLUTION: the sum of a number and its square is 20, find the numbers?

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Question 463583: the sum of a number and its square is 20, find the numbers?
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

let number be x
if the sum of a number and its+square is 20, you have
x%2Bx%5E2=20
x%5E2%2Bx-20=0..use quadratic formula
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x+=+%28-1+%2B-+sqrt%28+1%5E2-4%2A1%2A%28-20%29+%29%29%2F%282%2A1%29+
x+=+%28-1+%2B-+sqrt%28+1%2B80%29+%29%2F2+
x+=+%28-1+%2B-+sqrt%28+81%29+%29%2F2+
x+=+%28-1+%2B-+9+%29%2F2+

solutions:
x+=+%28-1+%2B+9+%29%2F2+
x+=+8%2F2+
x+=+4+
or
x+=+%28-1+-9+%29%2F2+
x+=+-10%2F2+
x+=-5+

check:
if x+=+4+:x%2Bx%5E2=20...-> 4%2B4%5E2=20.-> 4%2B16=20.-> 20=20

if x+=+-5+:-5%2B%28-5%29%5E2=20...-> -5%2B25=20.-> 20=20