d^2+2d=99

Solution for d^2+2d=99 equation:

Simplifying
d2 + 2d = 99

Reorder the terms:
2d + d2 = 99

Solving
2d + d2 = 99

Solving for variable 'd'.

Reorder the terms:
-99 + 2d + d2 = 99 + -99

Combine like terms: 99 + -99 = 0
-99 + 2d + d2 = 0

Factor a trinomial.
(-11 + -1d)(9 + -1d) = 0

Subproblem 1
Set the factor '(-11 + -1d)' equal to zero and attempt to solve:

Simplifying
-11 + -1d = 0

Solving
-11 + -1d = 0

Move all terms containing d to the left, all other terms to the right.

Add '11' to each side of the equation.
-11 + 11 + -1d = 0 + 11

Combine like terms: -11 + 11 = 0
0 + -1d = 0 + 11
-1d = 0 + 11

Combine like terms: 0 + 11 = 11
-1d = 11

Divide each side by '-1'.
d = -11

Simplifying
d = -11
Subproblem 2
Set the factor '(9 + -1d)' equal to zero and attempt to solve:

Simplifying
9 + -1d = 0

Solving
9 + -1d = 0

Move all terms containing d to the left, all other terms to the right.

Add '-9' to each side of the equation.
9 + -9 + -1d = 0 + -9

Combine like terms: 9 + -9 = 0
0 + -1d = 0 + -9
-1d = 0 + -9

Combine like terms: 0 + -9 = -9
-1d = -9

Divide each side by '-1'.
d = 9

Simplifying
d = 9
Solution
d = {-11, 9}