Question

What did I do wrong in this exponential equation? Please help!!

Answer 1

4x^2/3 + 5x^1/3 - 6 = 0

Let k = x^1/3

4k^2 + 5k – 6 = 0

(must use factoring)

4k^2 +8k – 3k – 6 = 0
(4k – 3) (K+2) = 0

K = ¾
K = -2

X^1/3 = ¾
x = 27/81

or

X ^ 1/3 = -2
x = -8



APPARENTLY -8 isnt an answer ! Why not???

Answer 2

x=27/64 not 27/81

Answer 3

oh yes sorry my bad , never mind that, but why can't it be -8 as well?

Answer 4

i think because the function on top does not have a solution at x=-8 in other words y is not equal to zero and it does not cross the x axis at that value so that solution is neglected this often happens a lot try graphing that and you will see it is right

Answer 5

x = -8 is in fact a solution. x^(1/3) = -2, x^(2/3) = 4.

Hence 4x^2/3 + 5x^1/3 - 6 = 4x4 + 5x(-2) - 6 = 16 - 10 - 6 = 0.

Answer 6

u know what it does cross the x axis at x=-8 i just graphed it on my calculator you should check it again they are both solutions

Answer 7

Thank you....but apparently the answer is only 27/64 ugh

Answer 8

what domain are you working with maybe your answer suppose to be anything greater than zero

Answer 9

We have just proved that -8 is a solution, so in this case the answers are wrong or the question asks explicitly for positive values of x.

Answer 10

is this a word problem how did you arrive at the top equation because a lot of word problems tend to neglect negative solutions

Answer 11

we're just learning exponential equations we aren't into quadratic equations much yet that's why we're supposed to factor

Answer 12

the question was the one I stated above..

Answer 13

thanks for helping

Answer 14

no worries