Question

Difficulty: MediumSimplifying Expressions and Combining Like Terms

Which of the following is equivalent to the expression 4x2(x−2y)−3x(x2−3xy)−(x3+xy2)4x^2(x - 2y) - 3x(x^2 - 3xy) - (x^3 + xy^2) for all real values of xx and yy?

  1. A
    x2y+xy2x^2y + xy^2
  2. B
    −17x2y−xy2-17x^2y - xy^2
  3. C
    −x3+x2+x2y−xy2-x^3 + x^2 + x^2y - xy^2
  4. x2y−xy2x^2y - xy^2Answer
  5. E
    −17x2y+xy2-17x^2y + xy^2

Answer

The correct simplified expression is x2y−xy2x^2y - xy^2.
Distributing the terms yields 4x3−8x2y−3x3+9x2y−x3−xy24x^3 - 8x^2y - 3x^3 + 9x^2y - x^3 - xy^2. Grouping and combining like terms results in (4−3−1)x3+(−8+9)x2y−xy2=x2y−xy2(4-3-1)x^3 + (-8+9)x^2y - xy^2 = x^2y - xy^2.

Step-by-Step Solution

1
Distribute the term 4x24x^2 to the terms inside the first set of parentheses: 4x2(x−2y)4x^2(x - 2y).
4x3−8x2y4x^3 - 8x^2y
Multiplying a monomial by a binomial requires distributing the multiplier to each term inside.
2
Distribute the term −3x-3x to the terms inside the second set of parentheses: −3x(x2−3xy)-3x(x^2 - 3xy).
−3x3+9x2y-3x^3 + 9x^2y
Carefully apply the distributive property, remembering that multiplying a negative term by a negative term yields a positive term: −3x⋅(−3xy)=9x2y-3x \cdot (-3xy) = 9x^2y.
3
Distribute the negative sign (or −1-1) to the terms inside the third set of parentheses: −(x3+xy2)-(x^3 + xy^2).
−x3−xy2-x^3 - xy^2
Distributing the negative sign changes the signs of all terms inside the parentheses.
4
Combine all parts and group the like terms: x3x^3, x2yx^2y, and xy2xy^2.
x2y−xy2x^2y - xy^2
Add the coefficients of the terms with the same variable parts: (4−3−1)x3+(−8+9)x2y−xy2=0x3+x2y−xy2=x2y−xy2(4 - 3 - 1)x^3 + (-8 + 9)x^2y - xy^2 = 0x^3 + x^2y - xy^2 = x^2y - xy^2.

Key Concept

Simplifying algebraic expressions by distributing and combining like terms.
Estimated Time:1m 0s
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