The value of a is 9, the correct option is B.
Given
Hank’s teacher asked him to verify that the product (y−3)(y2+3y+9), is a difference of cubes.
<h3>Quadratic equation;</h3>
The equation which has the highest degree is 2 is called quadratic equation;

Where a, b, and c are the constants.
The given polynomial is;

On multiplying the terms;

On comparing;

Hence, the value of a is 9.
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brainly.com/question/6169816