Question

An expression is given: 2(√k-1) +√8. If on adding -8√2 to the expression results in a rational number, what is the value of k?
A.6
B.12
C.18
D.36

Answer 1

answer .. K value is = 18 .

correct option is : C

Answer 2

Concept:

An expression is a combination of symbols, variables and mathematical operations.

Given:

2(√k - 1) + √8

Find:  

We are asked to find out the value of k.

Solution:

We have,

2(√k - 1) + √8

Now,

According to the question,

Adding ( - 8√2 ) to the 2(√k - 1) + √8,

i.e.

= 2(√k - 1) + √8 + ( - 8√2 )

= 2√k - 2 + √8 - 8√2

Rewrite,

= 2√k - 2 + 2√2 - 8√2

= 2√k - 2 - 6√2

Now,

For makking it rational number ,

Let,

2√k = 6√2

√k = 3√2

⇒

k = (3√2)²

k = 18

Hence we can say that the value of k is 18.

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