If coefficient of X^3 and X^4 in expansion of (1+ax+bX^2)(1-2X)^18 in power of X both are zero, then (a,b) equals to ?
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https://www.meritnation.com/ask-answer/question/if-1-ax-bx2-1-2x-18-be-expressed-in-ascending-powers-o/binomial-theorem/3335789