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(12.5^(1/2) + 12.5^(1/2))^2 - (25^(1/2))^2 =

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Bunuel
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(12.5^(1/2) + 12.5^(1/2))^2 - (25^(1/2))^2 = [#permalink] New post   24 Jul 2019, 02:51
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\((\sqrt{12.5} + \sqrt{12.5})^2 - (\sqrt{25})^2 =\)

(A) 0
(B) 5
(C) 12.5
(D) 25
(E) 50
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D
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lacktutor
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Re: (12.5^(1/2) + 12.5^(1/2))^2 - (25^(1/2))^2 = [#permalink] New post   24 Jul 2019, 02:59
(2√12.5)^2–(√25)^2= 4*12.5–25=50-25=25

The answer choice is D

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Re: (12.5^(1/2) + 12.5^(1/2))^2 - (25^(1/2))^2 = [#permalink] New post   24 Jul 2019, 03:02
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Bunuel wrote:
\((\sqrt{12.5} + \sqrt{12.5})^2 - (\sqrt{25})^2 =\)

(A) 0
(B) 5
(C) 12.5
(D) 25
(E) 50



\((\sqrt{12.5} + \sqrt{12.5})^2 - (\sqrt{25})^2 = 2\sqrt{12.5})^2 - 25 = (\sqrt{50})^2 -25 = 50 -25 = 25\)

IMO D
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Luca1111111111111
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Re: (12.5^(1/2) + 12.5^(1/2))^2 - (25^(1/2))^2 = [#permalink] New post   26 Jul 2019, 07:14
Kinshook wrote:
Bunuel wrote:
\((\sqrt{12.5} + \sqrt{12.5})^2 - (\sqrt{25})^2 =\)

(A) 0
(B) 5
(C) 12.5
(D) 25
(E) 50



\((\sqrt{12.5} + \sqrt{12.5})^2 - (\sqrt{25})^2 = 2\sqrt{12.5})^2 - 25 = (\sqrt{50})^2 -25 = 50 -25 = 25\)

IMO D

How to understand that that twice the root out of 12.5 equals 50?
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Luca1111111111111
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Re: (12.5^(1/2) + 12.5^(1/2))^2 - (25^(1/2))^2 = [#permalink] New post   26 Jul 2019, 07:15
lacktutor wrote:
(2√12.5)^2–(√25)^2= 4*12.5–25=50-25=25

The answer choice is D

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Can you please explain why 4*12.5?
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Re: (12.5^(1/2) + 12.5^(1/2))^2 - (25^(1/2))^2 = [#permalink] New post   26 Jul 2019, 07:20
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Luca1111111111111 wrote:
lacktutor wrote:
(2√12.5)^2–(√25)^2= 4*12.5–25=50-25=25

The answer choice is D

Posted from my mobile device

Can you please explain why 4*12.5?


(2√12.5)^2= (2^2)*(√12.5)^2=4*12.5=50

Hope it helps
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Re: (12.5^(1/2) + 12.5^(1/2))^2 - (25^(1/2))^2 = [#permalink]
26 Jul 2019, 07:20
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