Combined integer exponent laws
All variables here are nonzero. Signed indices are an intermediate calculation; the final expression is written with positive indices
- Add indices for a product The same rule applies to positive, zero and negative integer indices \(\displaystyle x^{-2}x^5=x^{-2+5}=x^3\)
- Subtract the denominator index Subtracting a negative index is different from subtracting its magnitude \(\displaystyle \frac{x^{-2}}{x^{-5}}=x^{-2-(-5)}=x^3\)
- Multiply inside a power Multiply each inner index by the outer index before combining factors \(\displaystyle (x^{-2})^3=x^{-6}\)
- Rewrite negative results A negative final index becomes a positive index in the denominator. All original variables remain nonzero \(\displaystyle 2x^{-3}y^2=\frac{2y^2}{x^3}\)
Worked example
Simplify. Assume x ≠ 0.
- \(\displaystyle -2-3=-5\)Subtract the denominator index
- \(\displaystyle \frac{2x^{-2}}{3x^3}=\frac23x^{-5}\)Divide the numerical coefficients separately
- \(\displaystyle \frac23x^{-5}=\frac{2}{3x^5}\)Move the negative-index factor to the denominator
Common mistakes
Difficulty levels
Questions about this topic
Why ask for signed indices before the final form?+
It separates the index calculation from rewriting reciprocal factors. Both steps matter
Why finish with positive indices?+
Positive indices show explicitly which factors are in the numerator and denominator. Signed indices are a useful intermediate calculation
Can I use a calculator?+
No. This topic is practised without a calculator
Which year level and chapter is this?+
Year 9 Mathematics, chapter 6: Indices and surds