Math Problem Statement

If a + b = 10 and a^2 + b^2 = 58, find: (a) a - b (b) a^3 + b^3

Solution

The question in the image asks you to solve for aba - b and a3+b3a^3 + b^3, given the following conditions:

  • a+b=10a + b = 10
  • a2+b2=58a^2 + b^2 = 58

Part (a) - Finding aba - b:

We know the identity: (a+b)2=a2+b2+2ab(a + b)^2 = a^2 + b^2 + 2ab

Substitute the known values into this equation:

102=58+2ab10^2 = 58 + 2ab 100=58+2ab100 = 58 + 2ab 2ab=10058=422ab = 100 - 58 = 42 ab=422=21ab = \frac{42}{2} = 21

Now use the identity for the difference of squares: (ab)2=(a+b)24ab(a - b)^2 = (a + b)^2 - 4ab

Substitute the values: (ab)2=1024×21(a - b)^2 = 10^2 - 4 \times 21 (ab)2=10084=16(a - b)^2 = 100 - 84 = 16 ab=16=4a - b = \sqrt{16} = 4

Thus, ab=4a - b = 4.

Part (b) - Finding a3+b3a^3 + b^3:

We use the identity for the sum of cubes: a3+b3=(a+b)((a+b)23ab)a^3 + b^3 = (a + b)((a + b)^2 - 3ab)

Substitute the known values: a3+b3=10((10)23×21)a^3 + b^3 = 10((10)^2 - 3 \times 21) a3+b3=10(10063)a^3 + b^3 = 10(100 - 63) a3+b3=10×37=370a^3 + b^3 = 10 \times 37 = 370

Thus, a3+b3=370a^3 + b^3 = 370.

Final Answers:

  • ab=4a - b = 4
  • a3+b3=370a^3 + b^3 = 370

Would you like further details or clarification on any of the steps?


Here are 5 related questions:

  1. How do you solve for aa and bb separately from the given equations?
  2. What is the geometric interpretation of a2+b2=58a^2 + b^2 = 58 in relation to the points (a,b)(a, b)?
  3. How can you extend this problem to complex numbers?
  4. What is the general formula for an+bna^n + b^n for any nn?
  5. Can the value of aba - b be negative? If so, under what conditions?

Tip: Always remember the common algebraic identities like the sum and difference of squares, cubes, etc., as they simplify many problems.

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Math Problem Analysis

Mathematical Concepts

Algebra
Sum and Difference of Squares
Sum of Cubes

Formulas

(a + b)^2 = a^2 + b^2 + 2ab
(a - b)^2 = (a + b)^2 - 4ab
a^3 + b^3 = (a + b)((a + b)^2 - 3ab)

Theorems

Algebraic Identities

Suitable Grade Level

Grades 9-11