If S = (4t + 3)(t – 2), find ds/dt when t = 5 secs.

Correct Answer: Option B

Explanation

(s = (4t + 3)(t – 2))

(frac{mathrm d s}{mathrm d t} = (4t + 3)(1) + (t – 2)(4))

= (4t + 3 + 4t – 8)

= 8t – 5

(frac{mathrm d s}{mathrm d t} (t = 5 secs) = 8(5) – 5)

= 40 – 5 

= 35 units per sec

There is an explanation video available below.