The difference of the square of a number and 28 is equal to 3 times that number. Find the negative solution.

Answer 1

"Difference" is just English for "subtract." The square of a number is that number multiplied by itself. Let's call the mystery number x, so the square of x is x².

The first half of the equation is x² - 28

The word "is" is the English for "equals." Therefore, the first half of the equation equals three times our mystery number.

x² - 28 = 3x

Now we need to factor.

x² - 3x - 28 = 0

(x - 7)(x + 4) = 0

x is either 7 or - 4. The questions asks for the negative answer, so we know:

x = - 4