If ` ( 1 + x - 2x^(2))^(20) = sum_(r=0)^(40) a_(r) x^(r) ` , then find   the value of ` a_(1)
Channel: Doubtnut
Date: 2020-05-24

If ` ( 1 + x - 2x^(2))^(20) = sum_(r=0)^(40) a_(r) x^(r) ` , then find   the value of ` a_(1) + a_(3) + a_(5) + …+ a_(39)` .