How would I solve this?

Ch 05 Sec 1 Ex 10 (a) - Determining a Formula Determine a formula for 1.2 + 2.3 + n.(n+1) (Enter the fraction in the form a/ b.) For n = 1, + + 1/2 1.2 2-3 n.(n+1) For n = 2, + + ... + E 1.2 2.3 n.(n+1) (Click to select) v For n = 3, 1.2 + = 2.3 ... + n.(n+1) (Click to select) For n = 4, 1 = 1.2 F 2.3 + ... + n.(n+1) (Click to select) For n = 5, 1.2 + 2.3 + n.(n+1) (Click to select) Identify the formula for the given sum, derived from the values obtained n = 1 to 5. O (n + 1) O (n - 1)/(n + 1) On/(n - 1) On/(n + 1) O (n + 2)/(n + 1)