SEAMO 2026 Paper F SET 1 – Self-practice Question 19

The polynomial $1-x+x^2-x^3+\cdots+x^8-x^9$ can be written as $a_0y^9+a_1y^8+a_2y^7+\cdots+a_8y+a_9$, where x=y−1. Find $|a_2|$.