Question bank/JEE Main/Mathematics

JEE MainMathematicsModerateBinomial Theorem

The sum of the
series 
 20C0− 20C1+ 20C2− 20C3+…+ 20C10 is \ ^{20}C_{0} - \ ^{20}C_{1} + \ ^{20}C_{2} - \ ^{20}C_{3} + \ldots + \ ^{20}C_{10}\ is\

Show answer and solution
(1+x)20= 20C0+ 20C1x+ 20C2x2+(1 + x)^{20} = \ ^{20}C_{0} + \ ^{20}C_{1}x + \ ^{20}C_{2}x^{2} +..... 20C20x20\ ^{20}C_{20}x^{20}
is

Put x = - 1

⇒0= 20C0− 20C1+ 20C2\Rightarrow 0 = \ ^{20}C_{0} - \ ^{20}C_{1} + \ ^{20}C_{2}.........− 20C9+ 20C10− 20C11+- \ ^{20}C_{9} + \ ^{20}C_{10} - \ ^{20}C_{11} +.....+ 20C20+ \ ^{20}C_{20}
⇒0=2( 20C0− 20C1+.……..− 20C9+ 20C10)− 20C10\Rightarrow 0 = 2\left( \ ^{20}C_{0} - \ ^{20}C_{1} +_{.}\ldots\ldots.. - \ ^{20}C_{9} + \ ^{20}C_{10} \right) - \ ^{20}C_{10}

Source: Grass-G / M-08 Mathematics Paper 23 October.docx

Need a video for this idea?

Scan any doubt from your notes and get a whiteboard explanation.