x = 7 + 4 \sqrt { 3 } , y = 7 - 4 \sqrt { 3 } \Rightarrow x ^ { - 2 } + y ^ { -2 } =

TS ICET 2017 Question Paper with Solutions for online practice

Question : 80 of 200

Marks: +1, -0

x = 7 + 4 √ { 3 }

, y = 7 -

4 √ { 3 } ⇒ x ^ { - 2 } + y ^ { -2 } =

Solution:

Given :

x=7+4√{3},y=7-4√{3}

x+y=14

xy=7^2-(4√3)^2=1

x^{-2}+y^{-2}={1}/{x^{2}}+{1}/{y^{2}}={x^{2}+y^{2}}/{x^{2}y^{2}}={(x+y)^{2}-2xy}/{(xy)^{2}}

={(14)^{2}-2×1}/{(1)^{2}}=196-2=194

Go to Question:

Prev Question

Next Question