Observation

The Chief Examiner observed that majority of the Candidates that attempted this question got it right.

They were able to express y + 𝛿𝑦=3(𝑥+𝛿𝑥)²+4(𝑥+𝛿𝑥)−1 after which they simplified

and found 𝛿𝑦 to be 𝛿𝑦=6𝑥𝛿𝑥+3(𝛿𝑥)²+4𝛿𝑥. Next, they divided all through by 𝛿𝑥 to obtain

^𝛿𝑦⁄_𝛿𝑥=6𝑥+3(𝛿𝑥)+4 after which they took the limit of both sides as 𝛿𝑥→0 and obtained

^𝛿𝑦⁄_𝛿𝑥=6𝑥+4.