Dividing 4x by 4 isolates x on one side of the equation
Average acceleration: ( v - v o ) / Δ t
v = 0 m/s, v o = 20 m/s, Δ t = 3.5 s
a (average) = ( 0 m/s - 20 m/s )/3.5 s = - 20 m/s / 3.5 s =
= - 5.7142857 m/s² ≈ - 5.71 m/s²
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Answer:

Step-by-step explanation:
Since we cannot factor the expression, we must use quadratic formula: 
Plug in <em>a</em> for 2, <em>b</em> for 3, and <em>c</em> for -7 and you should find your roots.