Vera Lee Man Er's answer to Luo Ruixiang's Secondary 3 A Maths question.
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For part i, you need to use cover up rule.
2/n(n+1)(n+2) = A/n + B/(n+1) + C/(n+2)
By cover up rule, A= 2/1(2) = 1
B = 2/(-1)(1) = -2
C = 2/(-2)(-1) = 1
Hence, answer is 1/n - 2/n+1 + 1/n+2
For part ii, refer to picture. You need to use summation
2/n(n+1)(n+2) = A/n + B/(n+1) + C/(n+2)
By cover up rule, A= 2/1(2) = 1
B = 2/(-1)(1) = -2
C = 2/(-2)(-1) = 1
Hence, answer is 1/n - 2/n+1 + 1/n+2
For part ii, refer to picture. You need to use summation
Date Posted:
7 years ago
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