Question

Suppose that y varies inversely with x. Given x=-3 when y=-105. Find y when x=15

Answer 1

Answer:

21

Step-by-step explanation:

It is given that y varies inversely with x.

$y\propto \dfrac{1}{x}$

$y=\dfrac{k}{x}$       ...(i)

where, k is constant of proportionality.

It is given that x=-3 when y=-105. Substitute these values in equation (i), to find the value of k.

$-105=\dfrac{k}{-3}$

$-105\times (-3)=k$

$315=k$

Now,

$y=\dfrac{315}{x}$

Substitute x=15 in the above equation.

$y=\dfrac{315}{15}$

$y=21$

Therefore, the value of y is 21 when x=15.