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root of 5 - root of 3
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03 Jun 2017, 08:13
03 Jun 2017, 08:13
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Question Stats:
70% (00:34) correct
29% (00:31) wrong based on 178 sessions
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\(( \sqrt{5} - \sqrt{3} )^2=\)
A) \(2 - 2 \sqrt{15}\)
B) \(2 - \sqrt{15}\)
C)\(8 - 2 \sqrt{15}\)
D) \(2\)
E) \(8 - 2 \sqrt{5}\)
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Re: root of 5 - root of 3
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06 Jun 2017, 15:59
06 Jun 2017, 15:59
1
Carcass wrote:
\(( \sqrt{5} - \sqrt{3} )^2 =\)
A) \(2 - 2 \sqrt{15}\)
B) \(2 - \sqrt{15}\)
C)\(8 - 2 \sqrt{15}\)
D) \(2\)
E) \(8 - 2 \sqrt{5}\)
Let's use the FOIL method.
(√5 - √3)² = (√5 - √3)(√5 - √3)
= √25 - √15 - √15 + √9
= 5 - 2√15 + 3
= 8 - 2√15
Answer: C
Re: root of 5 - root of 3
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27 Aug 2022, 21:06
27 Aug 2022, 21:06
1
Carcass wrote:
\(( \sqrt{5} - \sqrt{3} )^2=\)
Everyone knows these simple expansions
(a - b)(a - b) = aa + bb - 2ab
(a + b)(a + b) = aa + bb + 2ab
Just apply the first one for this question
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