Question

y is inversly proportional to x^3 y=28 when x=a work out the value of y when x=2a

Answer 1

Answer:

y = 7/2

Step-by-step explanation:

The above statement is written as

$y = \frac{k}{ {x}^{3} }$

where k is constant of variation

y = 28 x = a

$28 = \frac{k}{ {a}^{3} } \\ \\ k = 28 {a}^{3}$

The formula for the variation is

$y = \frac{28 {a}^{3} }{ {x}^{3} }$

when x = 2a

y is

$y = \frac{28 {a}^{3} }{( {2a)}^{3} } \\ y = \frac{ {28a}^{3} }{ {8a}^{3} } \\ \\ y = \frac{28}{8} \\ \\ y = \frac{7}{2}$

Hope this helps you