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Secondary 1 | Maths
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Secondary 1 chevron_right Maths chevron_right Singapore

pls help asap

Date Posted: 3 years ago
Views: 318
J
J
3 years ago
What's the issue? Don't understand the answer?
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3 years ago
it's okay I understand now sorry for the trouble
J
J
3 years ago
Ok, no worries. Was wondering why I got down voted and the request for new answer was put up.

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We notice the common pattern that as you move to the next term, 6 is subtracted.
So, what we want to do is to rewrite the first term in terms of subtracting a multiple of 6.
This way, we can link the term number to the expression.

Term 1 = 56 = 62 - 6 = 62 - 6 × 1
Term 2 = 50 = 62 - 6 - 6 = 62 - 6 × 2
Term 3 = 44 = 62 - 6 - 6 - 6 = 62 - 6 × 3
And so on. Notice that the multiple of 6 is always the same as the term number.
So for the nth term,
Term n = 62 - 6 × n = 62 - 6n
Next,
why is -283 not a term in the sequence?

What we want to do first is to equate -283 to the general term 62 - 6n. We solve for n.
-283 = 62 - 6n
-283 - 62 = -6n
-345 = -6n
n = -345/-6
n = 57.5 (or 57½)
The term numbers are all positive integers (in other words, natural numbers since start from 1st term, then go on to 2nd, 3rd, 4th, 5th,...)
But here we have 57½ which is a mixed number (or 57.5 which is a decimal)
Since these are not positive integerw, -283 is not a term in the sequence.
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J
J's answer
1022 answers (A Helpful Person)
1st
Well answered by J. Just to remove this question from the non-answered list.
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Arnold K H Tan
Arnold K H Tan's answer
2147 answers (A Helpful Person)