Question

Rewrite the exponential expression as a radical expression: $(3x+3)^{6/7}$

Original question: Rewrite the exponential expression as a radical expression.

(3x+3)6/7(3x+3)^{6/7}

729x6+7297\sqrt[7]{729x^6+729}

Expert Verified Solution

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Key concept: Fractional exponents of the form m/nm/n convert to radicals by using the denominator as the root index and the numerator as the power.

Step by step

Use the rule

am/n=amn.a^{m/n}=\sqrt[n]{a^m}.

For

(3x+3)6/7,(3x+3)^{6/7},

the denominator 77 means a seventh root, and the numerator 66 stays as the power:

(3x+3)6/7=(3x+3)67.(3x+3)^{6/7}=\sqrt[7]{(3x+3)^6}.

So the radical form is

(3x+3)67.\boxed{\sqrt[7]{(3x+3)^6}}.

Pitfall alert

A common error is expanding (3x+3)6(3x+3)^6 incorrectly or rewriting it as 729x6+7297\sqrt[7]{729x^6+729}. The exponent 66 applies to the entire binomial 3x+33x+3, not separately to each term inside the sum.

Try different conditions

If the expression were (3x+3)1/7(3x+3)^{1/7}, the radical form would be 3x+37\sqrt[7]{3x+3}. If it were (3x+3)8/7(3x+3)^{8/7}, it would become (3x+3)3x+37(3x+3)\sqrt[7]{3x+3} or (3x+3)87\sqrt[7]{(3x+3)^8} depending on the preferred form.

Further reading

fractional exponent, seventh root, power rule

FAQ

How do you rewrite $(3x+3)^{6/7}$ as a radical?

Use $a^{m/n}=\sqrt[n]{a^m}$. This gives $(3x+3)^{6/7}=\sqrt[7]{(3x+3)^6}$.

Why is $\sqrt[7]{729x^6+729}$ not correct?

Because the exponent $6$ must apply to the entire binomial $(3x+3)$, not to each term separately. Expanding inside the radical that way changes the expression.

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