Products and quotients of powers
An index counts repeated factors. For matching bases, multiplication adds positive indices and division subtracts them. Quotients require a nonzero original denominator
- Matching bases Keep the base and add the positive indices \(\displaystyle x^{3}\times x^{4}=x^{7}\)
- Quotient restriction Cancel only when the original denominator is nonzero \(\displaystyle \frac{x^{8}}{x^{3}}=x^{5},\quad x\ne0\)
- Coefficient arithmetic Multiply or divide coefficients independently of indices \(\displaystyle \frac{6a^{7}}{9a^{2}}=\frac23a^{5},\quad a\ne0\)
- Negative bases need brackets An even number of negative factors has a positive product; an odd number has a negative product \(\displaystyle (-3)^{2}=9,\quad(-3)^{3}=-27\)
- An outside minus stays outside Apply the power before the unbracketed negative sign \(\displaystyle -3^{2}=-9\)
Worked example
Simplify, retaining the original restriction x nonzero
- \(\displaystyle 8\div12=\frac23\)Simplify the numerical coefficient
- \(\displaystyle 3+4=7\)Add numerator indices
- \(\displaystyle 2+1=3\)Add denominator indices; x has index 1
- \(\displaystyle 7-3=4\)Subtract denominator total from numerator total
- \(\displaystyle \frac23x^{4},\quad x\ne0\)Combine the coefficient and power, preserving the original restriction
Common mistakes
Difficulty levels
Questions about this topic
Why do multiplication indices add?+
The product joins all factors from both powers. Two factors followed by three more gives five factors
Why does division subtract indices?+
Matching nonzero factors cancel in pairs. Subtract the denominator count from the numerator count
Can I combine powers with different bases?+
These two laws combine matching bases. Keep separate powers for different bases
What if the numerator index is equal to or smaller than the denominator index?+
Zero or negative indices arise. They are developed in the following sections, with a nonzero base
Does a negative base mean a negative answer?+
Not always. An even number of negative factors gives a positive product; an odd number gives a negative product
Can a coefficient be a fraction?+
Yes. Divide the numerical coefficients exactly and simplify the fraction; handle indices separately
Can I use a calculator?+
No. This topic is practised without a calculator
Which year level and chapter is this?+
Year 10 Mathematics, chapter 3: Algebra and indices