The expression
7b^3/(b^2 - 7b + 10)
will become undefined if the denominator is equal to 0. To find the excluded values, we must then equate the denominator to 0.
So,
b^2 - 7b + 10 = 0
Solving the quadratic equation will give the roots:
b = 5 and 2
Therefore, the excluded values are b = 5 and 2.