SOLUTION: how do you solve the Qudadratic Expression 16x^2-80x-12

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Question 26290: how do you solve the Qudadratic Expression 16x^2-80x-12
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
16x%5E2-80x-12
+4%284x%5E2-20x-3%29+

+4%284x%5E2-20x-3%29+. I cannot see this factorising easily, so resort to the quadratic formula.

x+=+%28-b+%2B-+sqrt%28b%5E2+-+4ac%29%29%2F%282a%29
x+=+%28-%28-80%29+%2B-+sqrt%28%28-80%29%5E2+-+4%2816%29%28-12%29%29%29%2F%282%2816%29%29
x+=+%2880+%2B-+sqrt%286400+%2B+768%29%29%2F%2832%29
x+=+%2880+%2B-+sqrt%287168%29%29%2F%2832%29

Now to try to simplify the square root. Start with an easy pair of factors like 4*1792 and build up to 16*448 etc, until you end up with a primary number... like the 7 below.

x+=+%2880+%2B-+sqrt%281024%2A7%29%29%2F%2832%29
x+=+%2880+%2B-+sqrt%281024%29sqrt%287%29%29%2F%2832%29
x+=+%2880+%2B-+32sqrt%287%29%29%2F%2832%29
x+=+%2880+%2B+32sqrt%287%29%29%2F%2832%29 OR x+=+%2880+-+32sqrt%287%29%29%2F%2832%29
x+=+%282.5+%2B+sqrt%287%29%29 OR x+=+%282.5+-+sqrt%287%29%29

jon.