1/2x^2+3/4x-1=0

-3/4(+-)SQRT((3/4^2)-4(1/2)(-1) / 2(1/2)

-3/4(+-)SQRT(9/16+2) / 1

This is as far as I can get I do not see any errors yet the answer is supposed to be

-3+-SQRT(41) /4

I am clueless as to where the 41 comes from

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- Jan 18th 2011, 12:06 PMKromletchQuadratic Formula
1/2x^2+3/4x-1=0

-3/4(+-)SQRT((3/4^2)-4(1/2)(-1) / 2(1/2)

-3/4(+-)SQRT(9/16+2) / 1

This is as far as I can get I do not see any errors yet the answer is supposed to be

-3+-SQRT(41) /4

I am clueless as to where the 41 comes from - Jan 18th 2011, 12:16 PMAckbeet
The original problem:

Quadratic formula gives

That's what I get. WolframAlpha gives the same.

I conclude your book's answer is wrong. - Jan 18th 2011, 12:29 PMKromletch
My apologies the books answer is yours as well i typed it incorrectly. How do you get (9 +32) / 16 out of 9/16+2

- Jan 18th 2011, 12:31 PMAckbeet
You have

This is the usual addition of fractions: get a common denominator and proceed. - Jan 18th 2011, 12:40 PMQuacky
Obviously it isn't necessary, but it would be easier to calculate if you multiplied the equation by four.

is so much easier to substitute into the formula, and it will probably*save*time as it's so much simpler to follow through. - Jan 18th 2011, 12:40 PMWilmer
To start, that should be: [-3 +- SQRT(41)] /4 ; the extra brackets are IMPORTANT.

GOOD IDEA to always get rid of fractions before doing anything else;

so multiply your equation by 4: 2x^2 + 3x - 4 = 0 : get the picture?

Now use the quadratic and you'll have no problems (Wink)