A quicker way to find the zeros of any equation is to use the zero function. In the hom screen go to F2--zeros(--then type in your equation then ,x) and tadaa. It's ike two strokes quicker, so it's not incredibly useful. Also, you want to do summation sequences or multiplication sequences, then you can find those under the F3 menu. it's a litt trick
for summation do as follows-- [sigma symbol](variable expression,variable,lower limit,upperlimit)