If a^2+1/a^2=79 where (a>0), find the value of a^3 +1/a^3

Note the binomial expansion,

(a + 1/a)³ = a ³ + 3a + 3/a + 1/a ³

so

a ³ + 1/a ³ = (a + 1/a)³ - 3 (a + 1/a)

Similarly,

(a + 1/a)² = a ² + 2 + 1/a ²

We're given a ² + 1/a ² = 79, so

(a + 1/a)² - 2 = 79

(a + 1/a)² = 81

a + 1/a = ±9

but a > 0, so we ignore the negative solution.

Then

a ³ + 1/a ³ = 9³ - 3×9 = 702

in mathematics, a function is a relationship between two variables such that the value of one of the variables, called the dependent variable, is determined by the value of the other variable, called the independent variable. there is a specific term we use to describe the set of independent variables of a function.

step-by-step explanation:

what grade level is this? need to know so i can look in my old textbooks!