what is the answer of (√5 + √7)² - (√12)²?
回答 (5)
2009-02-18 8:41 am
✔ 最佳答案
(5 +2√5√7 + 7) - (12) = 2√5√7 + 12- 12 =
2√5√7 =
2√35
2009-02-18 6:14 pm
(â5 + â7)^2 - (â12)^2
= (â5 + â7)(â5 + â7) - (â12)(â12)
= â(5 x 5) + â(7 x 5) + â(5 x 7) + â(7 x 7) - â(12 x 12)
= 5 + â35 + â35 + 7 - 12
= 5 + 7 - 12 + 2â35
= 12 - 12 + 2â35
= 2â35
= (â5 + â7)(â5 + â7) - (â12)(â12)
= â(5 x 5) + â(7 x 5) + â(5 x 7) + â(7 x 7) - â(12 x 12)
= 5 + â35 + â35 + 7 - 12
= 5 + 7 - 12 + 2â35
= 12 - 12 + 2â35
= 2â35
2009-02-18 4:44 pm
(â5 + â7)² - (â12)²
=(â5+â7)(â5+â7)- (â12)(â12)
=â25+â35+â35+â49 -â144
=5+2â35+7-12
=2â35 answer//
=(â5+â7)(â5+â7)- (â12)(â12)
=â25+â35+â35+â49 -â144
=5+2â35+7-12
=2â35 answer//
2009-02-18 4:41 pm
(sqrt 5 + sqrt 7)^2 = (sqrt 5)^2 + (sqrt 7)^2 + (2 x sqrt 5 x sqrt 7)
[as (a + b)^2 = a^2 + b^2 + 2ab]
= 5 + 7 + 2 x sqrt (5 x 7)
= 12 + 2 x sqrt 35
(sqrt 12)^2 = 12
thus (sqrt 5 + sqrt 7)^2 - (sqrt 12)^2 =
12 + 2 x sqrt 35 - 12
= sqrt 35 (answer)
[as (a + b)^2 = a^2 + b^2 + 2ab]
= 5 + 7 + 2 x sqrt (5 x 7)
= 12 + 2 x sqrt 35
(sqrt 12)^2 = 12
thus (sqrt 5 + sqrt 7)^2 - (sqrt 12)^2 =
12 + 2 x sqrt 35 - 12
= sqrt 35 (answer)
2009-02-18 4:39 pm
(root(5) +root(7))^2 - 12
(root(5) + root(7))(root(5)+root(7)) - 12
FOIL
5 + 7 + 2(root(5)root(7) - 12
2(root(35))
(root(5) + root(7))(root(5)+root(7)) - 12
FOIL
5 + 7 + 2(root(5)root(7) - 12
2(root(35))
收錄日期: 2021-05-01 12:06:05
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