I can't understand how I can find the X's here...

(x-4)(30/x+2)=30

Thanks

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- Apr 12th 2006, 06:18 AMdgolverkquadratic equations with fractions
I can't understand how I can find the X's here...

(x-4)(30/x+2)=30

Thanks - Apr 12th 2006, 06:29 AMCaptainBlackQuote:

Originally Posted by**dgolverk**

$\displaystyle

(x-4)(30/x+2)=30+2x-\frac{120}{x}-8=30

$.

Simplify a bit:

$\displaystyle

2x-\frac{120}{x}-8=0

$.

Multiply through by $\displaystyle x$:

$\displaystyle

2x^2-8x-120=0

$.

Now use the quadratic formula to solve for $\displaystyle x$

RonL - Apr 12th 2006, 07:06 AMdgolverk
well, it's the same way that I tried, but my answer isn't right according the answers book - it says that X=10 and X=-6

the book's answer is wrong? or I did something not right? - Apr 12th 2006, 07:54 AMearbothQuote:

Originally Posted by**dgolverk**

the bad news first: The answers in your book are right. Maybe you can demonstrate what you've done. Then it's much easier to help you.

Greetings

EB - Apr 12th 2006, 08:07 AMearbothQuote:

Originally Posted by**dgolverk**

that's what you should have done: Use the quadratic formula:

$\displaystyle x=\frac{-(-8) \pm \sqrt{64-4 \cdot 2 \cdot(-120)}}{2\cdot 2}$

$\displaystyle x=\frac{-(-8) \pm \sqrt{64+960}}{2\cdot 2}$

$\displaystyle x=\frac{-(-8) \pm 32}{2\cdot 2}$

$\displaystyle x=\frac{40}{4}\ \vee \ x=\frac{-24}{4}$

Greetings

EB - Apr 12th 2006, 08:59 AMdgolverkintersting...
I did exactly what you have done and got other answers..I guess I forgot something :rolleyes:

Thanks a lot!