I. Model Problems A monomial is an expression that is a number, variable or product of a number and variables. Examples of monomials: –3, 4x, 5xy, y2 To multiply monomials, multiply all the coefficients and all the variables. Example 1 Simplify 2x3(7x5). = 14x3x5
Multiply the coefficients.
= 14x8
Multiply variables.
The answer is 14x8. To divide monomials, divide the coefficients and the variables. 20x 7 y 6 Example 2 Simplify . 4x 2 y 5 Divide the coefficients. 5x 7 y 6 = 3 5 x y = 5x4y Divide variables. The answer is 5x4y. When you have power of a power, everything inside the parentheses gets raised to the power. You multiply exponents. Example 3 Simplify (5x2y4)3. = 53x2•3y4•3
Raise everything to the 3rd power.
= 125x6y12
Simplify.
The answer is 125x6y12.
To multiply rational expressions with monomials, in the numerator and the denominator, follow the rules of simplifying monomials. 15x 7 y 6 xy 6 Example 4 Multiply . 2x 2 y 5 5y 3 Multiply the numerators and the 15x 7 y 6 xy 6 = 2 5 denominators. 2x y 5y 3
3 6 4 x y . 2 (3x 2 y 3 )3 4x 2 y 5 Example 5 Multiply . 2x 2 y 5 18y 3 Simplify power to a power. 27x 6 y 9 4x 2 y 5 = 2x 2 y 5 18y 3 Multiply the coefficients and 108x 8 y14 = variables. 36x 2 y 8
The answer is
3x 8 y14 = 2 8 x y = 3x 6 y 6 The answer is 3x6y6.
III. Challenge Problems 23. What is the area of a rectangle with length 6xy7 inches and width (5x2y) inches? Write your answer as an expression in terms of x and y.
20x19 y 20 4x54 y19 z 20 (4x12 y19 z)3 24. Simplify . 8x17 y14 (2x 9 y15 )3 3x 4 y15 z 2
25. Correct the Error There is an error in the student work shown below: Question: (3x4y9)5 . Solution:
= (3x4y9)5 = 15x20y45
What is the error? Explain how to solve the problem. _________________________________________________________ _________________________________________________________
IV. Answer Key 1. 36x8 2. -63x12 3. -21x7 4. 60x13 5. 80x9y6 6. -12x18y20 7. 2x11 8. 2x5 9. 12x5 10. 5y8 11. 5x14y12 12. -6x17y31 13. 64x6y15 14. 32x15y10 15. -8x9y21 16. 49x4y2z8 17. 100x48y40 18. -27x15y30 19. (1/2)x6y11 20. (18/5)x6y4 21. 10x5y10 22. 4x9y8 23. 30x2y8 in2 24. (80/3)x61y22z21 25. The student multiplied the coefficient by the exponent instead of raising the coefficient to the power. The correct answer is 243x20y45.