Answer :

4x² - 100 = 0
     + 100  + 100
         4x² = 100
          4        4
           x² = 25
            x = +5
 4(5)² - 100 = 0
4(25) - 100 = 0
  100 - 100 = 0
               0 = 0

4(-5)² - 100 = 0
 4(25) - 100 = 0
   100 - 100 = 0
                0 = 0

The roots of the equation is positive or negative 5.
4x^2-100=0
4x^2=100
x^2=100/4
x^2=-25
x=5 or x=-5