Question 1177919


The area of a circle is given by the expression  

{{{16pi*x^2 -40pi*x +25pi}}}

since the area of a circle is {{{r^2*pi}}}, we can use it to find {{{r}}}

=> {{{r^2*pi=16pi*x^2 -40pi*x +25pi}}} .......simplify


{{{r^2=16x^2 -40x +25 }}}

{{{r^2=(4x)^2 -40x +5^2}}}

{{{r^2=(4x - 5)^2}}}

{{{r=4x - 5}}}


then, the circumference of this circle {{{2r*pi}}}

and an expression for the circumference of this circle will be

{{{2(4x - 5)pi}}}

{{{8x*pi - 10pi}}}