The demand function, x = $25/"p"^4$, 1 p 5
The elasticity demand, d= $- "p"/x * "dx"/"dp"$
x = $25/"p"^4$
x = 25 p-4
$"dx"/"dp" = (25)(-4)"p"^(-4-1)$
$= 25 xx -4 xx "p"^(-5)$
$= 25 xx (-4)xx1/"p"^5$
Hint for differentiation
$"d"/"dx"(1/"x"^"n") = "-n"/("x"^("n + 1"))$
x = $25/"p"^4$
$"dx"/"dp" = 25((-4)/"p"^5)$
d= $- "p"/x * "dx"/"dp"$
$= (-"p")/(25/"p"^4) xx 25 xx (-4)xx1/"p"^5$
$= (-"p"^5)/25 xx 25 xx (-4) xx 1/"p"^5$ = 4
