Which one is not a valid value of x?

Question

specek18 · Answer

attachment

specek18 · Answer

@satellite73

specek18 · Answer

@Jhannybean

specek18 · Answer

@DanJS pleaseeeeeeeeeeeeee help:(

undeadknight26 · Answer

May i just give you the answer?

specek18 · Answer

that'd be wonderful @undeadknight26

specek18 · Answer

@undeadknight26 what's the answer? sorry it's timed.

specek18 · Answer

@DanJS this is the problem...

danjs · Answer

did you just put in the numbers for x, and test which one is false?

specek18 · Answer

yeah that sounds right...could you help me?

danjs · Answer

or if you want to simplify it, you have to square both sides

freckles · Answer

you could get your like terms on one side
first subtract 12sqrt(x) on both sides
then you can square both sides

danjs · Answer

$$(\sqrt{x^2 - 10x - 25}+12\sqrt{x})*(\sqrt{x^2 - 10x - 25}+12\sqrt{x}) = (15\sqrt{x)}(15\sqrt{x)}$$

danjs · Answer

yeah i would do what you said first

specek18 · Answer

i just did that step on paper and i want to say it's 14.25

freckles · Answer

or...
$$\sqrt{x^2-10x+25}=3 \sqrt{x}$$
then square both sides

specek18 · Answer

is that correct?

danjs · Answer

yea

danjs · Answer

x^2 - 10x + 25 = 9x

specek18 · Answer

i'm stuck between A and b....

specek18 · Answer

@DanJS but a would be closer to factoring with 9...what answer should i go with?

danjs · Answer

it will be a decimal , so the quadratic equation would be used, and a calculator

danjs · Answer

i got x = 17.5777 or x = 1.4222

specek18 · Answer

ughhh. failed by one question...thank you to everyone for your help