z^3 + 3z^2 -25z - 75 = 0 Factor out common terms in the first two terms, then in the last two terms z^2(z+3)−25(z+3)=0 Factor out the common term z+3 (z+3)(z^2−25)=0 Ask: When will (z+3)(z^2−25) equal zero? When z+3=0 or z^2−25=0 Solve each of the 2 equations above z=−3,±5
