Question

If x/a = 4, a/y = 6, a2 = 9 and ab2 = −8 then x + 2y = ?

Select one:
A. −10
B. −15
C. −5
D. −13

Answer 1

-13

Explanation:

We are given:

`(x)/(a)=4`

`(a)/(y)=6`

`a^2=9`

`ab^2=-8`

Since
`ab^2=-8` then
`a` has to be negative.

Solving
`a^2=9` therefore gives
`a=-3`.

(Note:
`(-3)^2=(-3)(-3)=9`.)

`(x)/(a)=4` and
`a=-3` gives us:

`(x)/(-3)=4`.

Multiplying both sides by -3 gives:
`x=-12`.

`(a)/(y)=6` and
`a=-3` gives us:

`(-3)/(y)=6`.

Multiplying both sides by
`y` gives:
`-3=6y`.

Divide both sides by 6 gives:
`(-3)/(6)=y`.

Simplifying this gives us
`(-1)/(2)=y`.

Now we are asked to find the numerical value for
`x+2y`.

`-12+2((-1)/(2))`

`-12+-1`

`-13`

D.