The sum of a whole number and its square is 90. Find the number

-10 or 9

Step-by-step explanation:

Lets set it up like an equation

x + x^2 = 90

x^2 + x - 90 = 0

Use abc-formula

to find x = - 10 or 9

We put this into the original equation and find that both answers fit the equation

The number is 9.

Step-by-step explanation:

I've no idea how to show your work on this one, but here's my thought process:

I know that 81 is 9², and that their sum is 90.