If x^2 + 1/x^2 = 9, what is the value of x^4 + 1/x^4 ?  Choose the correct answer:
A) 10  B) 72  C) 79  D) 16  E) 18
IMPORTANT: I notice that if we SQUARE x², we get x⁴, and if we SQUARE 1/x², we get 1/x⁴, so let's see what happens if we take the equation x² + 1/x² = 9 andSQUAREboth sides:   (x² + 1/x²)²= 81   So, (x² + 1/x²)(x² + 1/x²) = 81   Expand to get: x⁴ + 1 + 1 + 1/x⁴ = 81   Simplify: x⁴ + 1/x⁴ = 79   Answer: 79
<result>C</result>
If x^2 + 1/x^2 = 9, what is the value of x^4 + 1/x^4 ?