Grade 10 — Mathematics 10C › C10U05 Exponents

GRADE 10 · ALBERTAOUTCOME AN3

L1 · Exponent Laws I: Products and Quotients

Learning goal

“I can multiply and divide powers that share a base by adding and subtracting exponents, I can show why the laws work using expanded form, and I can state why the base cannot be 0 in the quotient law.”

Base — the number or variable being repeatedly multiplied (the 3 in 3^5). In expanded form, it is the factor you see over and over.
Exponent — the small number that counts how many factors of the base are multiplied (the 5 in 3^5). In expanded form, it is a count, nothing more.
Power — the whole expression base^exponent, and also its value (3^5 is a power; 243 is its value).
Expanded form — a power written out as repeated multiplication: 3^5 = 3*3*3*3*3. Expanded form is the courtroom where every exponent law in this unit is proved.
Worked example

Simplify 2^3 * 2^2, and evaluate. Step 1: Expand both powers. 2^3 = 2*2*2 (three factors) and 2^2 = 2*2 (two factors). Step 2: Put them side by side: 2*2*2 * 2*2. Nothing has been multiplied together yet - it is one long string of factors of 2. Step 3: Count the factors: 3 + 2 = 5 factors. So 2^3 * 2^2 = 2^5, and 2^5 = 32. Check by values: 2^3 = 8 and 2^2 = 4, and 8 * 4 = 32. The law, stated: to multiply powers with the same base, keep the base and add the exponents - a^m * a^n = a^(m+n). The exponent is a factor count, and multiplying two strings of factors just joins the counts. Warning, said plainly: the law needs the same base. In 2^3 * 3^2 the factors are 2s and 3s; there is no single count to add, and no shortcut exists.

Check yourself — explain it

Why is 2^3 * 2^2 equal to 2^5 and not 2^6?

Paired problem — example still visible

Simplify x^4 * x^3 -> x^7 (four factors of x joined with three more: 4 + 3 = 7 factors)

Faded completion — last step is yours

"5^2 * 5^3: the first power has 2 factors of 5, the second has ___ factors, so in total there are ___ factors and the product is 5^___" -> 3; 5; 5

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.