Solve the equation: $1 + 4 + 7 + 10 + \ldots + x = 287$.

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Accepted Answer

Step 1: Let sum of $n$ terms $= 287$. $\frac{n}{2}[2 	imes 1 + (n - 1)3] = 287$
Step 2: $3n^2 - n - 574 = 0$
Step 3: $(3n + 41)(n - 14) = 0$. $n = 14$ (Reject $n = \frac{-41}{3}$)
Step 4: $x = a_{14} = 1 + 13 	imes 3 = 40$

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