14 less then the square of a number is the same as five times the number. find the number (it is negative)

Let's assume that the first number mentioned is x.

x^2 - 14 = 5x
x^2 - 5x - 14 = 0

From here you can factor or use the quadratic formula. Factoring is easier so:
(x - 7)(x+2) = 0 
=> x=7 or x=-2

Remember when factoring the factors of the constant have to add up to be the coefficient of x.

A= b/2 because u simplying both sides of equation