- Zero Product Property: if a × b = 0, then either a or b = 0 or both a and b = 0.
(Make sure to set f(x) to zero)
So for this equation, I will be factoring by grouping. Firstly, what two terms have a product of -5x^2 and a sum of 4x? That would be 5x and -x. Replace 4x with 5x - x: 
Next, factor 5x^2 + 5x and -x - 1 separately. Make sure that they have the same quantity on the inside: 
Now you can rewrite the equation as: 
Now apply zero product property to the factors to solve for x:

<u>The x-intercepts are (1/5 ,0) and (-1,0).</u>
In general, the sum of the measures of the interior angles of a quadrilateral is 360. This is true for every quadrilateral. This does not help here, because there are two angles (angles B and D) we know nothing about. We only know about opposite angles A and C.
In this case, you can use another theorem.
Opposite angles of an inscribed quadrilateral are supplementary.
m<A + m<C = 180
3x + 6 + x + 2 = 180
4x + 8 = 180
4x = 172
x = 43
m<A = 3x + 6 = 3(43) + 6 = 135
Answer: 135 deg