Answer:
a) 1/27
b) 16
c) 1/8
Step-by-step explanation:
a) 
One of the properties of the exponents tells us that when we have a negative exponent we can express it in terms of its positive exponent by turning it into the denominator (and changing its sign), so we would have:

And now, solving for x = 9 we have:

b) 
This is already a positive rational exponent so we are just going to substitute the value of y = 8 into the expression

c) 
Using the same property we used in a) we have:

And now, solving for z = 16 we have:

We must graph y=x^3-9x^2+11x+21. Please, see the attached file.
Then we see were the graph cuts the x-axis, and these values of x are the real solutions of the given equation:
The real solutions of the given equation are:x = -1, 3, and 7
Probably A I am not really sure I am trying sorry if it is wrong
Answer:
16/81
Step-by-step explanation:
(2/3)^4 = (2/3)*(2/3)*(2/3)*(2/3)
= 16/81