First you have to find something that multiplies to equal 9 and add to 10. 9 and 1 will do in this case. So next you have to factor the d^2 into 2 terms so you square root it to eliminate the square which leaves you with just d. Next look at your signs in the equation and as these are all positive the factor wil be positive. Now just add the two numbers you got,1 and 9, to d to get (d+1)(d+9)
