What is the smallest of 3 consecutive positive integers if the product of the smaller two is 5 less than 9 time the largest integer?

Given that the integers are consecutive, then:
suppose:
first number=x
second number=x+1
third number=x+2
the product of the first two is:
x(x+1)
Given that the product is 5 less than 5(x+2)
then
x(x+1)+5=5(x+2)
x^2+x+5=5x+10
simplifying the above we get:
x^2-4x-5=0
x=5 or x=-1
since the numbers are positive then the smallest number is 5

The answer is part a: use