Algebra and Trigonometry 10th Edition

$a=180$
According to the Binomial Theorem, the 3rd, that is, the ($2+1$)th term of $(x-2y)^{10}$ is: $_{10}C_2(x)^{10-2}(-2y)^2=\frac{10!}{(10-2)!\times2!}(x)^8(4)y^2=(45)x^8(4)y^2=180x^8y^2$ $ax^8y^2=180x^8y^2$ $a=180$