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M28-15
[#permalink]
16 Sep 2014, 01:28
16 Sep 2014, 01:28
2
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Expert Reply
Show timer
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A
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C
D
E
Difficulty:
25%
(medium)
Question Stats:
69% (01:03) correct
31%
(01:25)
wrong
based on 135
sessions
If \(x = (\sqrt{5} - \sqrt{7})^2\), which of the following is the best approximation of \(x\)?
A. \(0\)
B. \(1\)
C. \(2\)
D. \(3\)
E. \(4\)
A. \(0\)
B. \(1\)
C. \(2\)
D. \(3\)
E. \(4\)
Re M28-15
[#permalink]
16 Sep 2014, 01:29
16 Sep 2014, 01:29
1
Bookmarks
Expert Reply
Official Solution:
If \(x = (\sqrt{5} - \sqrt{7})^2\), which of the following is the best approximation of \(x\)?
A. \(0\)
B. \(1\)
C. \(2\)
D. \(3\)
E. \(4\)
\(x=(\sqrt{5}-\sqrt{7})^2=\)
\(=5-2\sqrt{35}+7=\)
\(=12-2\sqrt{35}\).
Since \(\sqrt{35}\approx{6}\), then \(12-2\sqrt{35}\approx{12-2*6}=0\).
Answer: A
If \(x = (\sqrt{5} - \sqrt{7})^2\), which of the following is the best approximation of \(x\)?
A. \(0\)
B. \(1\)
C. \(2\)
D. \(3\)
E. \(4\)
\(x=(\sqrt{5}-\sqrt{7})^2=\)
\(=5-2\sqrt{35}+7=\)
\(=12-2\sqrt{35}\).
Since \(\sqrt{35}\approx{6}\), then \(12-2\sqrt{35}\approx{12-2*6}=0\).
Answer: A
Re: M28-15
[#permalink]
18 Dec 2017, 08:54
18 Dec 2017, 08:54
Please could you elaborate on the solution?
I get that squaring the current equation will produce 5-7 but I do not understand where the 2xroot32 comes from. Is that not another way of producing root7 squared - which is already accounted for in the equation.
I get that squaring the current equation will produce 5-7 but I do not understand where the 2xroot32 comes from. Is that not another way of producing root7 squared - which is already accounted for in the equation.
