Question

PLEASE HELP!!!!! WILL MEDAL AND FAN!!!!!!!
Which is the extraneous solution of -x = √2x+15

(2x + 15 is under the √ sign. The entire right side of the equation is. Thanks)

Answer 1

what are your options?

Answer 2

Oh, sorry. lol

A. -5
B. -3
C. 3
D. 5

Answer 3

do you know what an extraneous solution is?

Answer 4

Root of a changed equation I believe.

Answer 5

yes, and it DOES NOT solve for the original equation.

Answer 6

I am pretty sure square both sides, then simplify to have x^2 - 2x - 15 = 0

Answer 7

yes, then find the solutions for x and whatever one does not work in the original is your answer

Answer 8

then it would be something like (x + or - ?)(x + or - ?)

Answer 9

?.. what do you mean?

Answer 10

?=some number, I am still working that one out. I learned that they need to be in two seperate parenthesis such as x ^2 + 8x + 15 would simplify to be (x + 5)(x + 3)

Answer 11

okay, to solve for x, using factoring like you're talking about, you need to find what 2 numbers multiply to get -15 but add up to get -2, since your equation is\[x^2-2x-15=0\]

Answer 12

-5 and 3 (x - 5) (x + 3) Which then would say that the answer is either x = 5 or x = -3

Answer 13

yes! now plug those into the original, and see which one does not work.

Answer 14

BECAUSE I subtracted/added the 5 and the 3 to 0 in seperate equations to get those two answers.

Answer 15

-3 does not.

Answer 16

yep! good job :)

Answer 17

Thanks! Here is the medal and fan....

Answer 18

There you go. Thanks again!!

Answer 19

thank you cx

Answer 20

and no problem

Answer 21

wait... I think that's wrong...

Answer 22

\[-(-3)=\sqrt{2(-3)+15}\]\[3=\sqrt{-6+15}\]\[3=\sqrt 9\]

Answer 23

Yes, it was wrong, but that is fine. :) I have a good enough grade in Algebra anyway. Thanks for the help though!