Question
$\sqrt[3]{-125a^6b^{12}}$
Original question:
Expert Verified Solution
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Key concept: This is a standard radical simplification problem. The key is to split the number and variables into perfect cubes, then take the cube root of each factor.
Step by step
Step 1: Rewrite the radicand as perfect cubes
= \sqrt[3]{(-5)^3(a^2)^3(b^4)^3}$$ because - $-125 = (-5)^3$ - $a^6 = (a^2)^3$ - $b^{12} = (b^4)^3$ ### Step 2: Take the cube root of each factor $$\sqrt[3]{(-5)^3(a^2)^3(b^4)^3} = -5a^2b^4$$ ### Final answer $$\boxed{-5a^2b^4}$$ ### Pitfall alert A common mistake is to treat cube roots like square roots and forget that odd roots preserve the sign of a negative number. Since this is a cube root, $\sqrt[3]{-125}=-5$, not $+5$. ### Try different conditions If the exponent on $b$ were not a multiple of 3, you would split it into a perfect cube times a leftover factor. For example, $\sqrt[3]{b^{13}}=b^4\sqrt[3]{b}$. ### Further reading cube root, perfect cube, radical simplificationFAQ
How do you simplify $\sqrt[3]{-125a^6b^{12}}$?
Rewrite the expression as $\sqrt[3]{(-5)^3(a^2)^3(b^4)^3}$, then take the cube root of each perfect cube to get $-5a^2b^4$.
Why is the result negative?
Because this is a cube root, and odd roots preserve the sign of a negative number. Since $-125=(-5)^3$, the cube root is $-5$.