How do we solve this C 2 2011 + C 5 2011 + C 8 2011 . . . . + C 100 T 2011 Share with your friends Share 0 Zuhaib Ul Zamann answered this Dear student, We consider the expansion of (1+x)2011=C0+C1x+...+C2011x2011Put x=1 we getC0+C1+C2+C3+...+C2011=22011 APut x=ωC0+C1ω+C2ω2+C3ω3+...+C2011ω2011=-ω4022=-ω2 BPut x=ω2 we getC0+C1ω2+C2ω4+C3ω6+...+C2011ω4022=-ω2011=-ω CA+ωB+ω2C givesC01+ω+ω2+C11+ω2+ω+C21+1+1+C31+ω+ω2+C41+ω2+ω+C51+1+1+...+C20111+ω2+ω=22011-1-1⇒3C2+C5+C7+...C2009=22011-2⇒6C2+C5+...+C1007=22011-2⇒C2+C5+...+C1007=22010-13Regards 0 View Full Answer