Math Problem Statement

If the sum of x and y is 8 and the product of x and y is 2 what is x cubed plus y cubed

Solution

Given the problem where the sum of xx and yy is 8, and the product of xx and yy is 2, we are asked to find x3+y3x^3 + y^3.

Step 1: Use the identities

We can use the identity for the sum of cubes: x3+y3=(x+y)(x2xy+y2)x^3 + y^3 = (x + y)(x^2 - xy + y^2) We know x+y=8x + y = 8 and xy=2xy = 2.

Step 2: Find x2+y2x^2 + y^2

We can use the identity: x2+y2=(x+y)22xyx^2 + y^2 = (x + y)^2 - 2xy Substitute the given values: x2+y2=822(2)=644=60x^2 + y^2 = 8^2 - 2(2) = 64 - 4 = 60

Step 3: Substitute into the sum of cubes formula

Now substitute into the formula for x3+y3x^3 + y^3: x3+y3=(x+y)(x2xy+y2)x^3 + y^3 = (x + y)\left(x^2 - xy + y^2\right) x3+y3=8(602)=8(58)=464x^3 + y^3 = 8(60 - 2) = 8(58) = 464

So, x3+y3=464x^3 + y^3 = 464.

Would you like any more details or have any questions? Here are 5 related questions to consider:

  1. How would the solution change if the sum of xx and yy were different?
  2. What are the values of xx and yy that satisfy these conditions?
  3. How would you approach this problem if only given the sum or the product of xx and yy?
  4. What is the value of x4+y4x^4 + y^4 using the same approach?
  5. How can the discriminant of the quadratic equation derived from these values help find xx and yy?

Tip: Remember that identities like x2+y2=(x+y)22xyx^2 + y^2 = (x + y)^2 - 2xy can simplify calculations involving sums and products of roots.

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Math Problem Analysis

Mathematical Concepts

Algebra
Polynomials

Formulas

Sum of cubes formula
Difference of squares formula

Theorems

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Suitable Grade Level

Grades 9-12