Math Problem Statement

a^1/3 +b^1/3 +c^1/3=(2^1/3 -1)^1/3 find 3(a+b+c)

Solution

Let's solve the given problem step by step.

Problem:

a1/3+b1/3+c1/3=(21/31)1/3a^{1/3} + b^{1/3} + c^{1/3} = (2^{1/3} - 1)^{1/3} We need to find 3(a+b+c)3(a + b + c).

Solution:

  1. Let x=a1/3x = a^{1/3}, y=b1/3y = b^{1/3}, and z=c1/3z = c^{1/3}. The equation can be rewritten as: x+y+z=(21/31)1/3x + y + z = (2^{1/3} - 1)^{1/3}

  2. Cubing both sides to eliminate the cube roots: (x+y+z)3=((21/31)1/3)3(x + y + z)^3 = \left((2^{1/3} - 1)^{1/3}\right)^3 Simplifying the right side gives: (x+y+z)3=21/31(x + y + z)^3 = 2^{1/3} - 1

  3. Expanding the left-hand side: x3+y3+z3+3(xy+yz+zx)(x+y+z)=21/31x^3 + y^3 + z^3 + 3(xy + yz + zx)(x + y + z) = 2^{1/3} - 1 Since x3=ax^3 = a, y3=by^3 = b, and z3=cz^3 = c, we have: a+b+c+3(xy+yz+zx)(x+y+z)=21/31a + b + c + 3(xy + yz + zx)(x + y + z) = 2^{1/3} - 1

    This expression simplifies if we can identify xy+yz+zxxy + yz + zx and x+y+zx + y + z. However, we need to find a+b+ca + b + c from this.

  4. Now, let's try to assume symmetric values for xx, yy, and zz. If we find a solution where x=y=zx = y = z, then we can proceed further. Let x=y=zx = y = z, which implies: 3x=(21/31)1/33x = (2^{1/3} - 1)^{1/3}

  5. Solving for xx: x=(21/31)1/33x = \frac{(2^{1/3} - 1)^{1/3}}{3}

  6. Substituting back, we get: a+b+c=3x3a + b + c = 3x^3

Thus, to find 3(a+b+c)3(a + b + c), we have: 3(a+b+c)=9x33(a + b + c) = 9x^3

Using our assumption, x=(21/31)1/3/3x = (2^{1/3} - 1)^{1/3} / 3.

Hence: 3(a+b+c)=9((21/31)1/33)3=(21/31)3(a + b + c) = 9 \cdot \left( \frac{(2^{1/3} - 1)^{1/3}}{3} \right)^3 = (2^{1/3} - 1)

So, the final answer is: 3(a+b+c)=21/31\boxed{3(a + b + c) = 2^{1/3} - 1}

Would you like more details or have any other questions?

Related Questions:

  1. How do we solve equations involving cube roots effectively?
  2. What are the steps for expanding expressions of the form (x+y+z)3(x + y + z)^3?
  3. Can we generalize this method to higher powers (e.g., fourth roots)?
  4. What are some properties of cube roots that simplify equations?
  5. How do we check if a cubic equation has a unique real solution?

Tip: When dealing with roots of higher degree (like cube roots), it can help to try symmetric substitutions or specific values to simplify the problem.

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Math Problem Analysis

Mathematical Concepts

Algebra
Cube Roots
Symmetric Substitution

Formulas

(x + y + z)^3 = x^3 + y^3 + z^3 + 3(xy + yz + zx)(x + y + z)

Theorems

Properties of Cube Roots

Suitable Grade Level

Grades 10-12