Thread: Tricky solution set.

The solution set for the equation: x - 4 - square root of(9x) = 0 consists of:


A) exactly one negative number
B) exactly one positive number ---Answer
C) exactly on positive number and one negative number.
D) exactly two negative numbers.
E) exactly two positive.


B) is the answer, but I have no idea why and neither does my dad, can someone please help me with this?

Are you positive that there is only one positive answer? because I got two positive answers. x=16 and x=1

It says that question 25.'s (this question) answer is B.

So I'm pretty sure... but could you show me what you did? Because I didn't even get that close to an answer.

Thanks for the speedy reply.


Edit: Nevermind I get what you did! 1 doesn't work because 1-4-3= -6 not 0

so can you show me how you got 16 ?

Sure,

x - 4 - sqrt(9x) = 0 add sqrt(9x) to both sides
x - 4 = sqrt(9x) now square both sides
x^2 - 8x + 16 = 9x subtract 9x from both sides
x^2 - 17x + 16 = 0 factor the left hand side
(x - 16) (x - 1) = 0 set both values equal to 0
x = 16 x = 1

I didn't even remember to check the answers. good job, there's your answer. 16 works, but not 1

I forgot one of the most basic things in Algebra, gosh I feel dumb.


Thank you!!