#1**0 **

We can use the binomial theorem, which is explained here --> https://www.mathsisfun.com/algebra/binomial-theorem.html

Since we're only finding the coefficient of y^{4}, the exponent of the y is, well 4, while the exponent of the 7 is 1 (5-4).

This means the y^{4} term is 5C1 * (2y)^{4}-7^{1}

= 5(2y)^{4}-7

= -35(2y)^{4}

= -560y^{4}

Which means the coefficient of y^{4} is -560, which is also your answer :)

Logarhythm Feb 14, 2021