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Arggg I suck at math... Help please!

V

Vortex22

Diamond Member
Ok, I'm stuck on these two algebra problems.

This one looks incredibly simple, but I can't figure it out:

Find a negative solution of x^2 = -23x + 60

It looks like a quadratic, but the answer I get when I plug it into the quadratic formula is incorrect. (this is online homework btw, I don't know the correct answer, I only know that I'm wrong 🙁 )

And the other one is 11/x-1 + 9/x+1 = 1/x^2-1, where x is in the form A/20, I have to find A
Note: the last denominator is x to the 2nd power minus 1, only the 2 is an exponent.

I multiplied the 1st fraction by (x+1) and the second by (x-1) and got a final answer of A=3/20 but this is incorrect. I probably look like a total moron, but I hate math 😛

I usually figure this stuff out on my own, but I can't get these 2 for some reason.

Thanks in advance for any help
🙂
 
Find a negative solution of x^2 = -23x + 60

It looks like a quadratic, but the answer I get when I plug it into the quadratic formula is incorrect. (this is online homework btw, I don't know the correct answer, I only know that I'm wrong )
Click to expand...
it is quadrtic. change it into standrd form like x^2 + 23x - 60 = 0 then solve like that

would be really simple if it were -23x and +60... but for this yo'l have to use the formula i think
 
Originally posted by: dighn
Find a negative solution of x^2 = -23x + 60

It looks like a quadratic, but the answer I get when I plug it into the quadratic formula is incorrect. (this is online homework btw, I don't know the correct answer, I only know that I'm wrong )
Click to expand...
it is quadrtic. change it into standrd form like x^2 + 23x - 60 = 0 then solve like that

would be really simple if it were -23x and +60... but for this yo'l have to use the formula i think
Click to expand...

I get x=-25.37 when I do this.
After plugging it into the equation I get 643.6369=643.51 😕
It might just be the calculator that is causing the small difference though.
 
Originally posted by: Vortex22
Originally posted by: dighn
Find a negative solution of x^2 = -23x + 60

It looks like a quadratic, but the answer I get when I plug it into the quadratic formula is incorrect. (this is online homework btw, I don't know the correct answer, I only know that I'm wrong )
Click to expand...
it is quadrtic. change it into standrd form like x^2 + 23x - 60 = 0 then solve like that

would be really simple if it were -23x and +60... but for this yo'l have to use the formula i think
Click to expand...

I get x=-25.37 when I do this.
After plugging it into the equation I get -643.6369=643.51 😕
Click to expand...

x^2 cannot be negative for real x's
 
Originally posted by: dighn
Originally posted by: Vortex22
Originally posted by: dighn
Find a negative solution of x^2 = -23x + 60

It looks like a quadratic, but the answer I get when I plug it into the quadratic formula is incorrect. (this is online homework btw, I don't know the correct answer, I only know that I'm wrong )
Click to expand...
it is quadrtic. change it into standrd form like x^2 + 23x - 60 = 0 then solve like that

would be really simple if it were -23x and +60... but for this yo'l have to use the formula i think
Click to expand...

I get x=-25.37 when I do this.
After plugging it into the equation I get -643.6369=643.51 😕
Click to expand...

x^2 cannot be negative for real x's
Click to expand...

Yeah I was putting -25.37^2 instead of (-25.37)^2 into the calc. But that wasn't what was causing my problems before, I just forgot to type it like that.

 
Well, I guess -25.37 is the correct answer for #1. Thanks

#2 is annoying me even more since I actually got an answer that appeared in the correct form after working through the problem, but it's still wrong 🙁
 
Ok I'm not really sure how to go about doing this problem the correct way but:

11/x-1 + 9/x+1 = 1/x^2-1

11(x+1)/(x-1)(x+1) + 9(x-1)/(x+1)(x-1) = 11x+11/x^2-1 + 9x-9/x^2-1

Add the fractions since the denom is now the same...

20x+2/x^2-1 = 1/x^2-1 ... -1/20?

Well, I screwed something up somewhere since last time I did it, I ended up with 20x-2 which made it 20x/x^2-1 = 3/x^2-1, then I just divided to get 3/20.

So, umm, yeah like I was saying... I suck at math.
 
Originally posted by: Vortex22
Ok I'm not really sure how to go about doing this problem the correct way but:

11/x-1 + 9/x+1 = 1/x^2-1

11(x+1)/(x-1)(x+1) + 9(x-1)/(x+1)(x-1) = 11x+11/x^2-1 + 9x-9/x^2-1

Add the fractions since the denom is now the same...

20x+2/x^2-1 = 1/x^2-1 ... -1/20?

So, umm, yeah like I was saying... I suck at math.
Click to expand...

-1/20 looks right to me but dont forget that's x, you need to find A still (but that's much easier)
 
Originally posted by: Vortex22
Ok the correct answer to #2 is confirmed as -1/20... I was just a moron and screwed up a sign somewhere before.
Click to expand...

don't forget you said #2 is asking for A in x = A/20
 
recognize that (x^2 - 1) = (x+1) * (x-1). multiply everything through by (x^2 - 1), and that will get rid of all the fractions, leaving you with a quadratic equation.
 
Originally posted by: dighn
Originally posted by: Vortex22
Ok the correct answer to #2 is confirmed as -1/20... I was just a moron and screwed up a sign somewhere before.
Click to expand...

don't forget you said #2 is asking for A in x = 20/A
Click to expand...

They just wanted the numerator as in A/20.

I put in -1 and it said correct so I'm happy 😀
 
Originally posted by: oog
recognize that (x^2 - 1) = (x+1) * (x-1). multiply everything through by (x^2 - 1), and that will get rid of all the fractions, leaving you with a quadratic equation.
Click to expand...

Ahh this was probably the *official* correct way to do it.

Thanks.
 
sorry, you don't even have a quadratic equation after multiplying everyting through by (x^2 - 1)
 
for #2

goes like this:

[11/(x-1)] + [9/(x-1)] = [1/(x^2 - 1)]

the right hand side factors out to:
1/(x-1)(x+1)

so multiply thru by the denominator and you get:

11(x+1) + 9(x-1) = 1
11x + 11 + 9x - 9 = 1
20x = -1
x = -1/20

-doug
 
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