Chapter 8: Problem 33
Solve. $$ t^{2 / 3}+t^{1 / 3}-6=0 $$
Short Answer
Expert verified
The solutions are t = 8 and t = -27.
Step by step solution
01
Identify Substitution
Let's simplify the equation by substituting a new variable. Let us set \[ u = t^{1/3} \] Then the equation becomes: \[ u^2 + u - 6 = 0 \]
02
Solve the Quadratic Equation
We now solve the quadratic equation \( u^2 + u - 6 = 0 \). This can be factored as: \[ (u - 2)(u + 3) = 0 \]. Therefore, we have: \[ u - 2 = 0 \] or \[ u + 3 = 0 \] which gives the solutions \[ u = 2 \] or \[ u = -3 \]
03
Substitute Back
Recall that \( u = t^{1/3} \). We substitute back to find the values of \( t \): \[ t^{1/3} = 2 \] which yields \[ t = 2^3 = 8 \] and \[ t^{1/3} = -3 \] which yields \[ t = (-3)^3 = -27 \]
04
Check Solutions
We check both solutions by plugging them back into the original equation:\( t = 8 \): \[ 8^{2/3} + 8^{1/3} - 6 = 4 + 2 - 6 = 0 \] This is correct.\( t = -27 \): \[ (-27)^{2/3} + (-27)^{1/3} - 6 = 9 - 3 - 6 = 0 \] This is also correct.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic equation
A quadratic equation has the general form \( ax^2 + bx + c = 0 \). It is called 'quadratic' because 'quad' means square, referring to the variable’s highest exponent. In our exercise, the quadratic equation is the transformed equation \( u^2 + u - 6 = 0 \) after substitution.
This simplified form helps us solve the original problem easier.
Solving a quadratic equation typically involves three methods:
This simplified form helps us solve the original problem easier.
Solving a quadratic equation typically involves three methods:
- Factoring,
- Using the quadratic formula,
- Completing the square.
substitution method
The substitution method involves replacing a complex expression with a simpler variable, which makes the equation easier to handle. In our exercise, we started with the equation \( t^{2/3} + t^{1/3} - 6 = 0 \) and set \( u = t^{1/3} \). This turned our equation into \( u^2 + u - 6 = 0 \).
By using substitution:
After solving for 'u', we did a 'reverse substitution' to find the values for 't' by solving \( t^{1/3} = u \).
By using substitution:
- We made the problem simpler and more recognizable.
- The quadratic form was easier to solve.
After solving for 'u', we did a 'reverse substitution' to find the values for 't' by solving \( t^{1/3} = u \).
factoring
Factoring is one of the methods used to solve quadratic equations, by expressing the quadratic as a product of linear factors. For the equation \( u^2 + u - 6 = 0 \), our goal was to express it in the form of \( (u - a)(u + b) = 0 \). We found that the factors were \( u - 2 \) and \( u + 3 \), simplifying the equation to \( (u - 2)(u + 3) = 0 \).
This allowed us to easily identify the solutions: \( u = 2 \) and \( u = -3 \).
Factoring works by:
This allowed us to easily identify the solutions: \( u = 2 \) and \( u = -3 \).
Factoring works by:
- Finding two numbers that multiply to give the constant term (in our case '-6')
- And adding to give the coefficient of the 'u' term (which is '1').