Question

81y square -k ={ 9y +1/2 } {9y -1/2} find the value of k​

Answer 1

Step-by-step explanation:

81y²-k

= (9y)²- ( √k)²

( 9y+√k) ( 9y-√k)= (9y+1/2) ( 9y-1/2)..............given

comparing ,

√k= 1/2

thus k = 1/4

Answer 2

Answer: k=$\frac{1}{4}$

Step-by-step explanation:

• This is clearly an formulae based question.
• We know $(a^{2}-b^{2} )=(a+b)(a-b)$
• Given, $81y^{2}-k=(9y+\frac{1}{2} ) (9y-\frac{1}{2} )$
• Taking, LHS:-

       $(9y+\frac{1}{2} ) (9y-\frac{1}{2} )$

    ⇒ $81y^{2}-\frac{1}{4}$                 [∵ $(a^{2}-b^{2} )=(a+b)(a-b)$ ]

Comparing with RHS we get

 ∴ k=$\frac{1}{4}$

• Hence, the value of K is $\frac{1}{4}$.

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