Question

se f(2x+1)=x²+1,o valor de f(9)é:
a)( )5
b)( )4
c)( )17
d)( )9

Answer 1

$f(2x+1) = x^{2} +1$

$y=2x+1$
$2x=y-1$
$x= \frac{y-1}{2}$
$f^{-} = \frac{x-1}{2}$

$f(x) = ( \frac{x-1}{2}) ^{2} +1$

$f(x) = \frac{ (x-1)^{2} }{4} +1$

$f(9)= \frac{ (9-1)^{2} }{4} +1$

$= \frac{64}{4} +1$

$= 16+1 =17$