Pikachu007
How I solved it was x^4 - x^3 - 6x^2 = 0 now as per the normal formula sum of roots is -b/a which is 1 so I marked that answer - why is that wrong
Bunuel
Official Solution:
If \(x = \sqrt[4]{x^3 + 6x^2}\), what is the sum of all possible values of \(x\)?
A. \(-2\)
B. \(0\)
C. \(1\)
D. \(3\)
E. \(5\)
Begin by raising the given expression to the 4th power: \(x^4 = x^3 + 6x^2\);
Next, rearrange the equation and factor out \(x^2\): \(x^2(x^2 - x - 6) = 0\);
Now, factorize the expression: \(x^2(x - 3)(x + 2) = 0\);
This results in three roots: \(x = 0\), \(x = 3\), and \(x = -2\). However, \(x\) cannot be negative since it is equal to the 4th root of an expression (\(\sqrt[4]{\text{expression}} \geq 0\)), which is always non-negative. Therefore, only two solutions are valid: \(x = 0\) and \(x = 3\).
The sum of all possible solutions for x is \(0 + 3 = 3\).
Answer: D
First of all, we have a 4th-degree equation, not a quadratic.
We get: \(x^2(x^2 - x - 6) = 0\). So, \(x = 0\), or solve \(x^2 - x - 6 = 0\), which gives \(x = 3\) and \(x = -2\).
Yes, the sum of the roots of \(x^2 - x - 6\) is 1, but as shown in the solution, \(x = -2\) is not valid because it does not satisfy the original equation \(x = \sqrt[4]{x^3 + 6x^2}\). The right-hand side is always non-negative, so \(x\) must be \(\geq 0\).
Please review the discussion for more clarity.