Question

Difficulty: MediumMultiplying Polynomials

Expand the given product of a binomial and a trinomial, combine like terms, and determine the values of the missing coefficients.

Answer:When the expression (3x−5)(2x2+4x−7)(3x - 5)(2x^2 + 4x - 7) is fully expanded and simplified, the resulting polynomial in standard form is 6x3+6x^3 + 【2】 x2+x^2 + 【-41】 x+35x + 35.

Answer

The coefficient for the x^2 term is 2, and the coefficient for the x term is -41.
By distributing each term of the binomial (3x−5)(3x - 5) to every term of the trinomial (2x2+4x−7)(2x^2 + 4x - 7), we get six terms. Grouping and combining the like terms yields an x2x^2 coefficient of 12−10=212 - 10 = 2 and an xx coefficient of −21−20=−41-21 - 20 = -41.

Step-by-Step Solution

1
Distribute the first term of the binomial, 3x3x, to each term in the trinomial.
3x(2x2)+3x(4x)+3x(−7)=6x3+12x2−21x3x(2x^2) + 3x(4x) + 3x(-7) = 6x^3 + 12x^2 - 21x
To apply the distributive property for the first part of the polynomial multiplication.
2
Distribute the second term of the binomial, −5-5, to each term in the trinomial.
−5(2x2)−5(4x)−5(−7)=−10x2−20x+35-5(2x^2) - 5(4x) - 5(-7) = -10x^2 - 20x + 35
To apply the distributive property for the second part, being careful to carry the negative sign.
3
Combine the results and group the like terms.
6x3+(12x2−10x2)+(−21x−20x)+356x^3 + (12x^2 - 10x^2) + (-21x - 20x) + 35
To arrange the expression so that coefficients of terms with the same exponent can be simplified.
4
Simplify the grouped terms.
6x3+2x2−41x+356x^3 + 2x^2 - 41x + 35
By adding the coefficients: 12−10=212 - 10 = 2 and −21−20=−41-21 - 20 = -41.

Key Concept

Distributive Property with Polynomials

Alternative Method

You can use the 'box method' (a grid) by creating a 2x3 table with 3x3x and −5-5 on the rows, and 2x22x^2, 4x4x, and −7-7 on the columns. Multiply the row and column headers to fill each cell, then add all the cells together along the diagonals to combine like terms.
Estimated Time:1m 30s
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