Question #78619
2 Answers
Aug 24, 2017
Explanation:
For low powers you can make use of Pascal's Triangle but I'll do it more generally here with the binomial theorem:
where
Hence, we have
we evaluate this, noting that
Aug 24, 2017
Explanation:
#"to expand "(x+a)^3" in general"#
#x^3+(a+a+a)x^2+(a^2+a^2+a^2)x+a^3#
#"here "a=-7#
#rArr(x-7)^3#
#=x^3+(-7-7-7)x^2+(49+49+49)x+(-7)^3#
#=x^3-21x^2+147x-343#