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secondary 3 | A Maths
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Date Posted: 2 years ago
Views: 357
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times 【a+b√7】at both sides of "="
2+4√7 = (4-√7)∙(a+b√7)
2+4√7 = (7b+4a) + (4b-a)∙(√7)
-7b + 4a = 2 ①
4b - 1a = 4 ③
16b - 4a = 16 ②
② + ①
9b = 16+2 = 18 ⇨ b = 2
⇨ ③
a = 4
times 【a+b√7】at both sides of "="
2+4√7 = (4-√7)∙(a+b√7)
2+4√7 = (7b+4a) + (4b-a)∙(√7)
-7b + 4a = 2 ①
4b - 1a = 4 ③
16b - 4a = 16 ②
② + ①
9b = 16+2 = 18 ⇨ b = 2
⇨ ③
a = 4
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