Uraniumfish SG When (1-x)(1+ax)^6 is expanded as far as the term term in x^2, the result is 1+bx^2. Find the possible values of a and b.
eagle SG = (1 - x)(1 + 6ax + 15a²x² + ...) = 1 + 6ax + 15a²x² - x - 6ax² + ... = 1 + (6a - 1) x + (15a² - 6a)x² + ... So, 6a - 1 = 0 a = 1/6 b = 15a² - 6a = 15/36 - 1 = -21/36 Did all mentally and without calculator... so do check prudently ;)
Uraniumfish SG = (1 - x)(1 + 6ax + 15a²x² + ...) = 1 + 6ax + 15a²x² - x - 6ax² + ... = 1 + (6a - 1) x + (15a² - 6a)x² + ... So, 6a - 1 = 0 a = 1/6 b = 15a² - 6a = 15/36 - 1 = -21/36 Did all mentally and without calculator... so do check prudently ;)Eagle, I love you.