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For the part (i), you gotta find 2 unknowns, a and d. So you need to form 2 equations and solve them simultaneously.

a+(9-1)d = 22 -----(Using the a+(n-1)d = an formula where n=9)
a+8d = 22 ---------(Equation 1)

(n/2)*(2a+(n-1)d = S
(4/2)*(2a+(4-1)d) = 49
4a+6d = 49 ---------(Equation 2)

Solving them simultaneously gives a =10, d = 3/2

(ii)
a+(n-1)d = an
10+(n-1)*3/2 = 46
(n-1)*3/2 = 36
n-1 = 24
n = 25
 
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