The correct option is B 5(2a 3) (2a 3) 20 a^2 45 =5(4a^2 9) #160; #160; #160; #160; #160; #160; #160; #160; #160; #160; # ...

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Ratio and Proportion

20 a2 - 45 =?

Question

$20 a^{2} - 45 =$ ?

5 (3 - 2 a) (3 + 2 a)

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5 (2 a - 3) (2 a - 3)

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3 (5 + 2 a) (5 - 2 a)

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3 (2 a + 5) (2 a - 5)

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Solution

The correct option is B $5 (2 a - 3) (2 a - 3)$
$20 a^{2} - 45 = 5 (4 a^{2} - 9)$
$= 5 [(2 a)^{2} - (3^{2})]$ .

We know, $a^{2} - b^{2} = (a + b) (a - b)$ .

Then, $20 a^{2} - 45$ $= 5 (2 a - 3) (2 a + 3)$ .

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