SOLUTION: can someone please show me how to solve this by using the quadratic formula and then prove my answer is correct, what is the quadratic formula. X^2-9=0

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Question 797112: can someone please show me how to solve this by using the quadratic formula and then prove my answer is correct, what is the quadratic formula.
X^2-9=0
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+x%5E2+-+9+=+0+
The quadratic formula applies to a parabola
which has the form:
+a%2Ax%5E2+%2B+b%2Ax+%2B+c+=+0+
The formula is:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
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You can make your equation into this form:
+1%2Ax%5E2+%2B+0%2Ax+-+9+=+0+
+a+=+1+
+b+=+0+
+c+=+-9+
Now plug these values into the formula
x+=+%28-0+%2B-+sqrt%28+0%5E2-4%2A1%2A%28-9%29+%29%29%2F%282%2A1%29+
+x+=+%28+0+%2B++sqrt%28+36+%29%29+%2F+2+
+x+=+6%2F2+
+x+=+3+
and, taking the negative square root,
++x+=+%28+0+-+sqrt%2836+%29+%29+%2F+2+
+x+=+-3+
The solutions are +x+=+3+, +x+=+-3+
check:
+x%5E2+-+9+=+0+
+3%5E2+-+9+=+0+
+0+=+0+
and
+%28-3%29%5E2+-+9+=+0+
+0+=+0+
OK