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2009-10-28T17:04:49+01:00
(√21 + √3)^2=21 + 2√63 + 3 = 24 + 2√63

(√15 - √5)^2= 15 -2√75 + 5 = 20 - 2√75
(√21-√20)(√21 + √20)= 21 - 20 =1

(a-3b)(a+3b)= a² - 9*b²
(1/2m + n^2)(1/2m-n^2)=¼m² - n⁴


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2009-10-28T17:28:53+01:00
(√21 + √3)^2=21 + 2√63 + 3 = 24 + 2√63

(√15 - √5)^2= 15 -2√75 + 5 = 20 - 2√75
(√21-√20)(√21 + √20)= 21 - 20 =1

(a-3b)(a+3b)= a² - 9*b²
(1/2m + n^2)(1/2m-n^2)=¼m² - n⁴