If f(x) varies directly with x and f(x)= 70 when x=5 , find the value of f(x) when x=9.XRound you final answer to the nearest whole number.

Question

asked Mar 23, 2023 144k views

1 Answer

MD Naseem Ashraf · Answer 1 · 2023-03-28T20:50:03+0000

Since f(x) varies directly with x, we can write

$f(x)=k\cdot x$

where k is the constant of proportionality. We know that when x=5, f(5)=70, then we have

$70=k\cdot5$

then, k is given as

$\begin{gathered} k=(70)/(5) \\ k=14 \end{gathered}$

Then, the equation which model the problem is

Now, we can substitute x=9 into this result. It yields,

$\begin{gathered} f(9)=14(9) \\ f(9)=126 \end{gathered}$

Therefore, the answer is 126