First of all, find the values of x (there are 2 because of the grade of inequation) for the inequation is annulled. For this reason, we transform the above inequation into an equation.
x^2 -4x -12 = 0
After that, forf finding the roots of the equation, we are using the following formula:
X1=[-b + (b^2 - 4ac)^1/2]/2a, where a=1, b=-4, c =-12
a,b,c being the coefficients of the equation above.
X2= [-b - (b^2 - 4ac)^1/2]/2a
after calculation
X1=6, X2=-2
After that, following the rule which says that between the two roots, the values of x have the opposite sign of the "a" coefficient, and outside the roots, the values of X have the same sign with the coefficient "a", we could find the conclusion that inequation is positive on the following intervals
(-ininite, -2) U (6, + infinite)
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