When 21 is subtracted from the square of a number, the result is 4 times the number. Find the negative solution.
Let's say the number is x.
According to the given conditions, we have the equation:
x^2 - 21 = 4x
Rearranging the equation:
x^2 - 4x - 21 = 0
To find the solutions to this quadratic equation, we can factorize it:
(x - 7)(x + 3) = 0
So, x = 7 or x = -3
Therefore, the negative solution is x = -3.