Answer:
Step-by-step explanation:
I'm sorry forgot how to exactly solve it
 
        
             
        
        
        
Answer:
If a is 1.. we substitute one in every a in g(a)
4 * 1 + 16
4+ 16 = 20
g(a)= 20
f(20)
-16 + 20 = 4
and 4/4 = 1
so f (g (a)) = a
Step-by-step explanation:
 
        
             
        
        
        
Answer:
b=12 
Step-by-step explanation:
a^2+b^2=c^2
(9×9) + b^2= 15×15
81+ b^2= 225
-81. -81
b^2=144
√. √
b= 12