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Help Leo Ng! Anyone can contribute an answer, even non-tutors.
help me. thanks
Date Posted: 5 years ago
Views: 462
Let first term be a and common difference be d.
Sum of odd terms: 140
1st + 3th + 5th + 7th + 9th + 11th + 13th
= 140
a + (a+2d) + (a+4d) + (a+6d) + (a+8d) + (a+10d) + (a+12d) = 140
7a + 42d = 140 ①
Sum of even terms: 160
2nd + 4th + 6th + 8th + 10th + 12th + 14th
= 160
a+d + (a+3d) + (a+5d) + (a+7d) + (a+9d) + (a+11d) + (a+13d) = 160
7a + 49d = 160 ②
② - ① :
7d = 20
d = 20/7
7a = 160 - 49(20/7) = 20
a = 20/7
Sum of odd terms: 140
1st + 3th + 5th + 7th + 9th + 11th + 13th
= 140
a + (a+2d) + (a+4d) + (a+6d) + (a+8d) + (a+10d) + (a+12d) = 140
7a + 42d = 140 ①
Sum of even terms: 160
2nd + 4th + 6th + 8th + 10th + 12th + 14th
= 160
a+d + (a+3d) + (a+5d) + (a+7d) + (a+9d) + (a+11d) + (a+13d) = 160
7a + 49d = 160 ②
② - ① :
7d = 20
d = 20/7
7a = 160 - 49(20/7) = 20
a = 20/7
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