Question

x square + 84 x - 160 =0

Answer 1

x² + 84x = 160 
x² + 84x - 160 = 0 

Here a quadratic equation formed :
Where 
a (coefficient of x²) = 1 
b (coefficient of x ) = 84
c (constant           ) = -160
D (Discriminant    ) = b² - 4ac
                               = 84² - 4 x 1 x 160 
                               = 7056 + 640 
                               = 7696

we are finding roots (zeros) of the quadratic by this quadratic formula
-b+-√D/2a 
Two zeros are 

160 - √7696 / 2  and 160 + √7696 / 2