Adam Ahmad Samdin's answer to Muhd Aiman's Junior College 1 H1 Maths question.
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Part (i) answer:
You can form 2 equations using the information given, using the formula for term of geometric series.
Using simultaneous equations, solve for r.
You will get 2 values of r, one positive and one negative. You need to test both and prove that your answer fulfill all requirements. We know that a must be positive since ar^4 is a positive number, and number x multiplied by a number to its even power will be positive assuming x is positive. If x is negative, it will be negative. Since ar^4 = 8, we can reject the negative solution of r with proof.
From there just plug r into either equation and solve for a.
You can form 2 equations using the information given, using the formula for term of geometric series.
Using simultaneous equations, solve for r.
You will get 2 values of r, one positive and one negative. You need to test both and prove that your answer fulfill all requirements. We know that a must be positive since ar^4 is a positive number, and number x multiplied by a number to its even power will be positive assuming x is positive. If x is negative, it will be negative. Since ar^4 = 8, we can reject the negative solution of r with proof.
From there just plug r into either equation and solve for a.
Date Posted:
6 years ago
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