[SPLIT] sqrtxsquared + 9x - 1 = x - 3: getting wrong ans.

[Guest]

sqrtxsquared + 9x - 1 = x - 3
(sqrtxsquared + 9x - 1)squared = (x - 3)squared
xsquared + 9x - = xsquared + 2x - 3x - 3x + 9
xsquared + 9x - 1 = xsquared - 5x + 9
9x - 1 = -5x + 9
14x = 10
x = 5/7

Please help!! When I plug in 5/7, I get a non-real answer.
Thank you for all your help!!!!

 

[stapel]

sqrtxsquared + 9x - 1 = x - 3

Does the above mean either of the following?

. . . . .sqrt[x²] + 9x - 1 = x - 3

. . . . .sqrt[x² + 9x - 1] = x - 3

Or something else? Are the instructions to "solve"?

Thank you.

Eliz.

P.S. The standard notation for exponents uses the carat symbol. For instance, "three squared" would be written as "3^2".

 

[Guest]

Hello,
Thank you for responding. I am new at this. I made a little error, sorry!
It should state sqrt(x^2+9x-1)=x-3.
Thank you again!!

 

[Denis]

It should state sqrt(x^2+9x-1)=x-3.

Rule: if you square sqrt(n), answer is n

So if you square sqrt(x^2 + 9x - 1), answer is x^2 + 9x - 1

Then you need to square the other side: (x - 3)^2 = x^2 - 6x + 9

So you now have:
x^2 + 9x - 1 = x^2 - 6x + 9

Can you finish it?

 

[Guest]

That was the last step I had but when you plug in the answer it does not work.
I am still lost!

 

[stapel]

That was the last step I had but when you plug in the answer it does not work. I am still lost!

We'll be glad to help you try to find any errors, but you'll need to provide a clear listing of your steps.

Thank you.

Eliz.

 

[Guest]

(sqrtx^2+9x-1)^2=(x-3)^2
x^2+9x-1=x^2+2x-3x-3x+9
x^2+9x-1=x^2-4x+9
9x-1=-5x+9
13x=10
x=10/13
Thanks!

 

[stapel]

(sqrtx^2+9x-1)^2=(x-3)^2
x^2+9x-1=x^2+2x-3x-3x+9

You might want to check your work on multiplying (x - 3)(x - 3).

Eliz.