Question

Metal and Fan


if x>0 and y>0 and x^9=4 and x^7=9/y^2, which of the following is an expression for the value of x in terms of y?

A) 4/9 y
B) 2/3 y
C) 3/2 y^2
D)6y
E) 36y^2

Answer 1

\[x^9 = 4\]\[x = 4^{1/9}\]\[x^7 = 4^{7/9}\]

Answer 2

man now I'm confused. Give me a few minutes to eat dinner, I'll get back to this later.

Answer 3

ok

Answer 4

I'm seriously stuck lol

Answer 5

Guys help!

Answer 6

isolate x first
then substitute?

Answer 7

\[x > 0\]
So obviously x is a number greater than zero.

\[y > 0\]
So obviously y is a number greater than zero.

*WE KNOW THAT ALREADY, NOTHING NEW*

Answer 8

We need to find x in terms of y.

Answer 9

\[\large x^7=9/y^2\]\[\large x= 4^{1/9}\]\[\large 4^{1/9} =\frac{9}{y^2}\]\[\large 4^{1/9}y^2 = 9\]\[\large y^2 = \frac{9}{4^{1/9}}\]\[\large y=\ ?\]

Answer 10

noo he needs y in terms of x.

Answer 11

-_- lol.

Answer 12

it's just a bunch of algebra, but idk why I'm stuck

Answer 13

sooooo you're solving for x?

Answer 14

Ohhh yeah you are lol duh

Answer 15

So it's going to be solved the other way around....

Answer 16

X^9 = 4 & X^7 = 9/Y^2 For the second equation multiply both sides by Y^2 to give:

X^9 = 4; X^7 x Y^2 = 9 Set them so they're equal

X^7 x Y^2 = [9/4] X^9 pull out the common factor X^7

Y^2 = [9/4] X^2 multiply by reciprocal and rearrange

X^2 = [4/9] Y^2 take square root

X = [2/3] Y

-SOURCE: YAHOO