Question

If x+1/x = 3 then x2+1/x2 =
(a) 6 (b) 7 (c) 8 (d) 9 ​

Answer 1

EXPLANATION.

⇒ (x + 1/x) = 3.

As we know that,

Squaring on both sides of the equation, we get.

⇒ (x + 1/x)² = (3)².

As we know that,

Formula of :

⇒ (x + y)² = x² + y² + 2xy.

Using this formula in the equation, we get.

⇒ (x)² + (1/x)² + 2(x)(1/x) = 9.

⇒ (x)² + (1/x)² + 2 = 9.

⇒ x² + 1/x² = 9 - 2.

⇒ x² + 1/x² = 7.

Option [B] is correct answer.

Answer 2

★ANSWER♥︎

x²+1/x² = 11

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❤︎Given

x-1/x = 3---(1)

On Squaring equation (1), we get

=> (x-1/x)² = 3²

=> x²+1/x²-2*x*(1/x) = 9

/* By algebraic identity:

(a-b)² = a²+b²-2ab */

=> x²+1/x² -2 =9

=> x² + 1/x² = 9+2

=> x² + 1/x² = 11

Therefore,

x²+1/x² = 11

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