1. ## quadratic equations with fractions

I can't understand how I can find the X's here...
(x-4)(30/x+2)=30

Thanks

2. Originally Posted by dgolverk
I can't understand how I can find the X's here...
(x-4)(30/x+2)=30

Thanks
Expand the brackets:

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

Simplify a bit:

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

Multiply through by $x$:

$
2x^2-8x-120=0
$
.

Now use the quadratic formula to solve for $x$

RonL

3. 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?

4. Originally Posted by dgolverk
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?
Hello,

Greetings

EB

5. Originally Posted by dgolverk
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?
Hello,

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

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

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

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

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

Greetings

EB

6. ## intersting...

I did exactly what you have done and got other answers..I guess I forgot something
Thanks a lot!