Answer:
The square root of 8 - 2√5 is
[tex] \sqrt{4 + \sqrt{11} } \: - \sqrt{4 - \sqrt{11} } [/tex]
Step-by-step explanation:
To find the square root
8-2√5 must be in the form √a - √b where a > b
√ 8 - 2√5 = √a - √b
Square both sides
8 - 2√5 = (√a - √b)²
That's
8 - 2√5 = (a + b) - 2√ab
Since the two surd expressions are equal we can equate them
That's
8 = a + b ........ 1
a = 8 - b ........ 2
2√5 = 2√ab
Simplify
Divide both sides by 2
√5 = √ab
square both sides
We have
5 = ab ....... 3
Substitute a = 8 - b into equation 3
5 = ( 8 - b)b
5 = 8b - b²
b² - 8b + 5 = 0
After solving
b = 4 + √ 11 or 4 - √ 1
Since b is less than a
b = 4 - √11
a = 4 + √11
So the square root of 8 - 2√5 is
[tex] \sqrt{4 + \sqrt{11} } \: - \sqrt{4 - \sqrt{11} } [/tex]
Hope this helps you.
