Question 604580
f(x)= 3(x^2+5) Find f^-1(x), f^-1(27)
.
Find f^-1(x):
y = 3(x^2+5)
switch the variables and solve for y:
x = 3(y^2+5)
x/3 = y^2+5
x/3 - 5 = y^2
sqrt(x/3 - 5) = y
or
{{{f^-1(x) = sqrt(x/3 - 5)}}}
.
finding f^-1(27):
{{{f^-1(x) = sqrt(x/3 - 5)}}}
{{{f^-1(27) = sqrt(27/3 - 5)}}}
{{{f^-1(27) = sqrt(9 - 5)}}}
{{{f^-1(27) = sqrt(4)}}}
{{{f^-1(27) = 2}}} (that's plus or minus 2)