# SAT exponents and radicals: rules with worked examples Source: https://1600.now/blog/sat-exponents-radicals --- SAT Math Simplify SAT exponents and radicals, convert fractional powers, and solve radical equations without losing restrictions. Written by [Luke Finigan](https://1600.now/about) 3 min read Updated Oct 2, 2026 Use exponent rules on factors with the same base. For radicals, pull out perfect powers and check solutions in the original equation after squaring. ### Choose the operation before the rule The expression $x^3x^4$ is a product, so it becomes $x^7$. The expression $x^3+x^4$ is a sum; adding the exponents would change its value. At $x=2$, the sum is $8+16=24$, while $2^7=128$. That one substitution catches the bad shortcut. Before simplifying, look at the main operation. Are you multiplying powers, dividing them, raising a power to another power, or adding terms? Most of the work happens in that decision. A long expression can contain several operations, so handle the parentheses first and apply one rule at a time. | Operation | Rule | Example | | --- | --- | --- | | Multiply like bases | $a^ma^n=a^{m+n}$ | $3^2\cdot3^4=3^6$ | | Divide like bases | $a^m/a^n=a^{m-n}$, $a\ne0$ | $x^7/x^2=x^5$, $x\ne0$ | | Power of a power | $(a^m)^n=a^{mn}$ | $(x^3)^4=x^{12}$ | | Negative exponent | $a^{-n}=1/a^n$, $a\ne0$ | $2^{-3}=1/8$ | | Zero exponent | $a^0=1$, $a\ne0$ | $7^0=1$ | Equivalent Expressions · Easy: Which expression is equivalent to $72x^2$? · A $72(1+x^2)$ B $(8x)(9x)$ C $(8x^2)(9x^2)$ D $(72x^2)(x)$ - [Open the question and explanation](https://1600.now/bank/math/e2459660) - [Practice equivalent expressions questions](https://1600.now/bank/math/skill/Equivalent%20expressions) - [Print the equivalent expressions worksheet](https://1600.now/sat-equivalent-expressions-worksheet) ### A simplification with several rules Simplify $\dfrac{(2x^3)^2}{4x^2}$ for $x\ne0$. First square both factors in the numerator: $(2x^3)^2=4x^6$. Then divide: $\dfrac{4x^6}{4x^2}=x^4$. The coefficient and variable need separate attention. Squaring $2x^3$ gives $4x^6$, not $2x^6$. Also, the simplified expression is still being used under the original restriction $x\ne0$. Canceling a denominator doesn't make the original expression defined at zero. Try a numerical check at $x=2$. The original is $16^2/16=16$, and the simplified expression is $2^4=16$. Checking one input won't prove an identity, but it can expose a missed coefficient or exponent. ### Rewrite both sides with the same base Solve $4^{x+1}=32$. Rewrite 4 as $2^2$ and 32 as $2^5$: $(2^2)^{x+1}=2^5$. That gives $2^{2x+2}=2^5$, so $2x+2=5$ and $x=3/2$. Equal powers of the same positive base other than 1 have equal exponents. Check the result: $4^{5/2}=(\sqrt4)^5=2^5=32$. Rewriting the bases gives an exact answer without estimating a logarithm from a graph. If you can't make the bases match naturally, don't invent an exponent rule that adds or multiplies different bases. ### Fractional exponents tell you the root For positive $a$, $a^{m/n}=\sqrt[n]{a^m}=(\sqrt[n]{a})^m$. The denominator names the root; the numerator names the power. Thus $27^{2/3}=(\sqrt[3]{27})^2=3^2=9$. A negative sign on the exponent adds a reciprocal: $16^{-3/4}=\dfrac{1}{(\sqrt[4]{16})^3}=\dfrac18$. It does not make the answer negative. Keep that distinction visible by writing the reciprocal before calculating. With real numbers, even roots require a nonnegative radicand. Odd roots can have negative radicands: $\sqrt[3]{-8}=-2$. If variables are involved, use the restrictions stated in the question rather than assuming they are positive. ### Pull perfect squares out of radicals For $\sqrt{72}$, factor $72$ as $36\cdot2$. Then $\sqrt{72}=\sqrt{36}\sqrt2=6\sqrt2$. A useful factorization leaves no perfect-square factor inside the radical. To add radicals, simplify first. $\sqrt{50}+\sqrt8=5\sqrt2+2\sqrt2=7\sqrt2$. You can add these because their remaining radicals match. You cannot turn $\sqrt2+\sqrt3$ into $\sqrt5$: squaring the first expression gives $5+2\sqrt6$, not $5$. For variables, $\sqrt{x^2}=|x|$. At $x=-4$, the square root is $4$. If the question states $x\ge0$, you may replace $|x|$ with $x$; without that information, keep the absolute value. ### Squaring an equation creates candidates Solve $\sqrt{x+6}=x$. Since a square root is nonnegative, any solution must satisfy $x\ge0$. Squaring gives $x+6=x^2$, or $(x-3)(x+2)=0$. The candidates are $3$ and $-2$. Substitute both into the original. At $x=3$, $\sqrt9=3$, so it works. At $x=-2$, $\sqrt4=2\ne-2$, so it fails. The answer is $3$. A graph can help identify candidates, but the original equation decides which ones survive. ### Practice the step you missed If you missed the coefficient, practice powers of products. If you kept an invalid root, practice radical equations with substitutions at the end. An error log that only says "radicals" is too broad to help tomorrow. Use [exponent practice](https://1600.now/sat-skill/equivalent-expressions) or select equivalent-expression questions in the [Math bank](https://1600.now/bank/math/browse). Redo a missed question without its explanation, then solve a different expression using the same rule. Write the restriction beside the first line, not after you have canceled it away. Try it yourself: For $x>0$, which expression equals $\dfrac{x^{3/2}}{x^{1/2}}$? · A $x$ B $x^2$ C $\sqrt{x}$ D $1$ Luke Finigan is a student developer and the creator of 1600.now, a free Digital SAT practice platform. [About Luke](https://1600.now/about). ### Keep reading - **[SAT quadratics: forms, roots, vertex, and solution counts](https://1600.now/blog/sat-quadratics-guide)** Choose the right quadratic form, solve exact roots, interpret the vertex, and use the discriminant and Desmos without losing restrictions. - **[SAT Math formulas: reference sheet and what to learn](https://1600.now/blog/sat-math-formulas)** Compare Bluebook reference formulas with algebra, percent, circle, and trig formulas to learn, then practice choosing the right one. [Browse SAT resources →](https://1600.now/sat-resources)