+0

# i need help

+7
111
2
+600

If $$f(x)=\frac{ax+b}{cx+d}, abcd\not=0$$ and $$f(f(x))=x$$ for all $$x$$in the domain of $$f$$, what is the value of $$a+d$$?

This was asked before but the thread got locked and no one provided a soluton

Jul 19, 2020

#1
0

If you try some cases, you'll find a + d = 1.

Jul 19, 2020
#2
+600
+7

that is the wrong answer, but it's ok! the answer is actually 0

Jul 19, 2020