MTH1W Algebraic Expressions & Exponent Laws
Grade 9 Unit 2 — practice questions with full solutions
Collecting like terms, the distributive property, multiplying and dividing monomials, and the exponent laws. This is the single most transferable skill set in the whole course.
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- Group the x terms and the y terms separately.
- x terms: 3x − 7x = −4x.
- y terms: 5y + 2y = 7y.
- Only like terms can be combined — x and y stay apart.
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- Distribute the 4: 8x − 12.
- Distribute the −2 — watch the sign on both terms: −2x − 10.
- Combine: 8x − 2x = 6x, and −12 − 10 = −22.
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- Multiply the coefficients: 3 × (−2) = −6.
- Add exponents on x: x2 × x1 = x3.
- Add exponents on y: y3 × y2 = y5.
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- Divide the coefficients: 12 ÷ 4 = 3.
- Subtract exponents on a: a5−2 = a3.
- Subtract exponents on b: b3−1 = b2.
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- A power outside a bracket applies to every factor inside.
- Apply it to the coefficient: 24 = 16.
- Apply it to the variable — multiply the exponents: (x3)4 = x12.
- A very common error is writing 2x12 and forgetting to raise the 2.
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- (a) Area of a rectangle is width × height. Region A: 3 × x = 3x. Region B: 3 × 5 = 15.
- (b) Total area = 3x + 15.
- The whole rectangle has height 3 and total width (x + 5), so its area can also be written as 3(x + 5).
- (c) Both expressions describe the same rectangle, so 3(x + 5) = 3x + 15 — this is exactly the distributive property, shown as area.
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- Substitute carefully, using brackets around the negative value: 5(−2)2 − 3(−2) + 2.
- Powers first: (−2)2 = 4, so the first term is 5(4) = 20.
- Second term: −3(−2) = +6.
- Add it all: 20 + 6 + 2.
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- Perimeter = 2(length) + 2(width).
- Substitute: 2(3x + 2) + 2(x − 1).
- Expand: 6x + 4 + 2x − 2.
- Collect like terms: 8x + 2.
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- All three are like terms, so just combine the fraction coefficients.
- Use a common denominator of 4: 2⁄4 + 3⁄4 − 1⁄4.
- That gives 4⁄4 = 1.
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- Multiply the numerator first — add exponents: a4+2b2+3 = a6b5.
- Now divide — subtract exponents: a6−3 = a3.
- And for b: b5−1 = b4.
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- Distribute the −2: −6a + 8b.
- Distribute the 5: +10a − 5b.
- The final bracket has an invisible −1 in front: −a − 3b.
- Collect a terms: −6a + 10a − a = 3a.
- Collect b terms: 8b − 5b − 3b = 0b, which vanishes.
MTH1W Algebraic Expressions & Exponent Laws — common questions
Short answers to the things students ask most about this unit.
What are the exponent laws in Grade 9 math?
Multiplying powers with the same base adds exponents; dividing subtracts them; a power of a power multiplies them; and anything to the power zero equals one.
Why is (2x³)⁴ not 2x¹²?
The exponent outside the bracket applies to every factor inside, including the coefficient. So 2 is also raised to the fourth power, giving 16x¹².
The classes teach the method behind every one of these.
The solutions above show the steps. The classes teach how to think about the problem in the first place — interactive, and worked through at the student’s own pace. Try 3 complete classes free — no payment required to begin.
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