How do you solve #d^2+56=-18d#?
First, we put it into the ‘standard’ quadratic formula form. Then we factor it into roots.
Even multiples of 56 are 2 and 4. Only 4 works with 14 to give us both the multiple (4*14) and the sum (4 + 14) that we need to satisfy the equation.
So our solutions (roots) are: d = -4 and d = -14.