The correct option is B { 9, 9} Given, y^2 81=0 ⇒ y^2 9y+9y 81=0 ⇒ y(y 9)+9(y 9)=0 ⇒ (y+9)(y 9)=0 ⇒ y+9=0 or y 9=0 ⇒ y ...

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Applications (Word Problem)

Solve for y...

Question

Solve for $y$ : $y^{2} - 81 = 0$

{- 1, 1}

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{9}

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{- 9, 9}

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{81}

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Solution

The correct option is B ${- 9, 9}$
Given, $y^{2} - 81 = 0$
$\Rightarrow y^{2} - 9 y + 9 y - 81 = 0$
$\Rightarrow y (y - 9) + 9 (y - 9) = 0$
$\Rightarrow (y + 9) (y - 9) = 0$
$\Rightarrow y + 9 = 0$ or $y - 9 = 0$
$\Rightarrow y = - 9$ or $y = 9$
Hence, required solution is ${- 9, 9}$ .
Thus option C is correct choice.

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