i found my mistake here
.........don't worry about the g .......g cancel out from equation 
12) is same as 11)......the only difference is u have to find initial speed instead of angle
........if u don't understand than i can explain u 
I LOVE YOU lol
just one doubt
why did we use -0.5 and 3.5
why not use 0.5 as positive and keep 3.5 as 4
will we get the same answer?