Question

binomial theorem

(2x - 5y)^7 

Answer 1

(2x)^7 + 7C1 (2x)^6 (-5y) +7C2 (2x)^5 (-5y)^2 + 7C3 (2x)^4 (-5y)^3 +7C4 (2x)^3 (-5y)4 +7C5 (2x)2 (-5y)^5 +7C6 (2x) (-5y)^6 + (-5y)7
=128 x7 - 7*64*5 x^6 y + 32*105 x5  y2 - 35* 16* 125 x4 y3 + 35*8*625 x3 y4 - 21 *3125 * x^2 y^5 + 7 * 2 * 625*25 y -35 y^7