A particle moves from a fixed point O on a straight line with an initial velocity of [math]2ms^{-1}[/math] .[br]Its acceleration, a [math]ms^{-2}[/math] at t seconds after passing through O is given by [math]a=4-6t[/math].
(a) the instantaneous velocity, in [math]ms^{-1}[/math] of the particle when [math]t=3[/math].
(b) the instantaneous velocity, in [math]ms^{-1}[/math] of the particle when [math]a=-8[/math]