Acceleration

Aprticle starts from rest and acceleration as shown in this graph

http://up.do7a.com/get-9-2008-do7a_com_1ofo7inw.jpg

http://up.do7a.com/get-9-2008-do7a_com_1ofo7inw.jpg

Determine 1-the particle’s speed at t=1s and at t=20s
2-distance traveled in the first 20sec

my answer:

1-
Vf=Vi+at
v=0+2x10=20 m/sec

2-???
3_??
How can I do it?

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Aprticle moves along the x axis according to the equation x=2+3t-1t^2
where x is in meters and t is in seconds
At t=3s find
1-the position of the praticle
2-its velocity
3- its acceleration

:my answer

1-
X=2+9-9=2m

2_??
X=(Vf+Vi/2)t
can I use this^^^^

3_??

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THis graph of Vx versus t for motion of amotorycleist line

http://up.do7a.com/get-9-2008-do7a_com_sejbpinj.jpg
http://up.do7a.com/get-9-2008-do7a_com_sejbpinj.jpg

1-find the average acceleration for the time interval t=0 to t=6
2-estimate the time at which the acceleration has its greatest positive value and the value of the acclereation at that instant
3-when is the acceleration zero?
4-estimate the maximum negative value of the acceleration and the time at which it occurs

I didn’t understand this Que