A dart is shot straight up from 1.5m above ground level. The distance d,(adsbygoogle = window.adsbygoogle || []).push({});

in meters, the dart is above ground at time t, in seconds, is :

d(t) = -4.9t^2 + 20t + 1.5

For how many seconds is the dart in the air?

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# Derivative question (Help Please)

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