What is the value of a in the polynomial

Answer: a= 16
Step-by-step explanation:
We have the following expression:
[tex](y-4)(y^2 +4y +16)[/tex]
To find the value of the coefficient "a" you must use the distributive property to multiply the expression:
[tex](y-4)(y^2 +4y +16)[/tex]
until you transform it to the form:
[tex]y^3 +4y^2 +ay -4y^2 -ay-64[/tex]
Then we have
[tex](y-4)(y^2 +4y +16)\\\\(y^3 +4y^2 +16y -4y^2 -16y-64)\\\\[/tex]
Therefore the value of a in the polynomial is 16