The following are rules regarding the multiplying of variable expressions.
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Rule 1: To multiply monomials with the same base, keep the base and add the powers:
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x ax b= x a + b
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Rule 2: To raise a base to a power, keep the base and multiply the powers.
- ( x a) b= x ab
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Rule 3: To raise a product to a power, raise each factor in the product to that power.
- ( xy) a= x ay a
Example 1
Simplify each of the following multiplication problems and state which of the preceding rules was applied.
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yy 5
- ( x 4) 3
- (–2 x 4 y 2 z 3) 5
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a 3( a 2 b 3) 4
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To multiply monomials together, follow this procedure.
- Multiply the numerical coefficients together.
- Multiply the variables together.
- Write the results as a product.
Example 2
Simplify each of the following.
- (4 x 2)(3 x 3)
- (–8 a 3 b 2)(2 a 2 b 2) 3
- (4 x 2)(3 x 3) = (4 × 3)( x 2 x 3) = 12 x 5
- (–8 a 3 b 2)(2 a 2 b 2) 3 = (–8 a 3 b 2)(8 a 6 b 6) = –64 a 9 b 8
To multiply polynomials together, multiply each term in one polynomial by each term in the other polynomial. Then simplify if possible.
Example 3
Multiply each of the following.
- 5 x(3 x 2 – 4 x + 2)
- (4 x – 2)(3 x + 5)
- ( x + y)( x 2 – xy + y 2)
The following shows how each equation is multiplied both horizontally and vertically.
Equation (a) done horizontally:
Equation (a) done vertically:
Equation (b) done horizontally:
Equation (b) done vertically:
Equation (c) done horizontally:
Equation (c) done vertically: