SOLUTION: Please help me solve- By quadratic equation formula, solve the following equations: (correct to 4 decimal places) (a) x square + 6x + 7 = 0 (b) 3x square - x - 7 = 0 (c) x squ

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Question 758657: Please help me solve-
By quadratic equation formula, solve the following equations: (correct to 4 decimal places)
(a) x square + 6x + 7 = 0
(b) 3x square - x - 7 = 0
(c) x square - 3x - 3.51 = 0
I know the quadratic formula but I put it in and the answers didn't match.
Please help me!
It is due very soon.
Thank You for your time :D

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

(a)
x%5E2+%2B+6x+%2B+7+=+0
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x+=+%28-6+%2B-+sqrt%28+6%5E2-4%2A1%2A7+%29%29%2F%282%2A1%29+

x+=+%28-6+%2B-+sqrt%2836-28+%29%29%2F2
x+=+%28-6+%2B-+sqrt%288+%29%29%2F2
x+=+%28-6+%2B-+2.8284%29%2F2
solutions:
x+=+%28-6+%2B+2.8284%29%2F2
x+=+%28-3.1716%29%2F2
x+=+-1.5858
or
x+=+%28-6+-+2.8284%29%2F2
x+=+%28-8.8284%29%2F2
x+=+-4.4142

(b)
3x%5E2+-+x+-+7+=+0
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x+=+%28-%28-1%29+%2B-+sqrt%28+%28-1%29%5E2-4%2A3%2A%28-7%29+%29%29%2F%282%2A3%29+

x+=+%281+%2B-+sqrt%281%2B84+%29%29%2F6
x+=+%281+%2B-+sqrt%2885+%29%29%2F6
x+=+%281+%2B-+9.2195%29%2F6
solutions:
x+=+%281+%2B+9.2195%29%2F6
x+=+10.2195%2F6
x+=1.7033
or
x+=+%281+-+9.2195%29%2F6
x+=+%28-8.2195%29%2F6
x+=+-1.3699

(c)
x%5E2+-+3x+-+3.51+=+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%28-3.51%29+%29%29%2F%282%2A1%29+
x+=+%283+%2B-+sqrt%289%2B14.04+%29%29%2F2+
x+=+%283+%2B-+sqrt%2823.04+%29%29%2F2+
x+=+%283+%2B-+4.8%29%2F2+
solutions:
x+=+%283+%2B+4.8%29%2F2+
x+=+7.8%2F2+
x+=+3.9+...to four decimal places x+=+3.9000+
or
x+=+%283+-+4.8%29%2F2+
x+=+-1.8%2F2+
x+=+-0.9+..to four decimal places x+=+-0.9000+