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WAEC SSCE - Further Mathematics - 2022 (Objective)

Question 1 Report

If \(U_n = kn^2 + pn\), \(U_1 = -1\), \(U_5 = 15\), find the values of k and p.

Answer Details

Un = kn2 2  + pn,

U1 1  = -1,

U5 5  = 15,

when n = 1
U1 = k(1)2 2 + p(1) = -1
k + p = -1 --------eqn1
when n = 5
U5 5  = k(5)2 2 + p(5) = 15
25k + 5p = 15 --------eqn2
multiply eqn1 by 5 and eqn2 by 1
5k + 5p = -5 -------eqn3
25k + 5p = 15 -------eqn4
eqn4 - eqn3
20k = 20
k = 1
sub for k in eqn1
1 + p = -1
p = -1 -1 = -2