Mathematics

Mathematics

Problem

Which of the following is the correct expansion of (x−y)3(x-y)^3? a) x3+3x2y+3xy2+y3x^{3}+3x^{2}y+3xy^{2}+y^{3} b) x3−3x2y−3xy2+y3x^{3}-3x^{2}y-3xy^{2}+y^{3} c) x3−3x2y+3xy2−y3x^{3}-3x^{2}y+3xy^{2}-y^{3} d) x3+y3−3xy(x−y)x^{3}+y^{3}-3xy(x-y)
Intuitive explanation

Expanding a binomial to the third power is about recognizing the pattern in how terms build up. Rather than multiplying (x−y)(x−y)(x−y)(x-y)(x-y)(x-y) three times, you can use the binomial theorem or recall that the coefficients follow Pascal's triangle (1, 3, 3, 1). The key insight is tracking both the powers of xx and yy as they decrease and increase, and carefully managing the negative sign on yy through each term.

Intuitive explanation

Expanding a binomial to the third power is about recognizing the pattern in how terms build up. Rather than multiplying (x−y)(x−y)(x−y)(x-y)(x-y)(x-y) three times, you can use the binomial theorem or recall that the coefficients follow Pascal's triangle (1, 3, 3, 1). The key insight is tracking both the powers of xx and yy as they decrease and increase, and carefully managing the negative sign on yy through each term.

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