If $f (x) = 7 x^{2} - 15$ , then find the value of $f (3)$ $-$ $f (5)$ .

102

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66

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- 112

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- 54

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Solution

The correct option is C $- 112$
Given $f (x) = x^{2} - 15$
Then $f (3) = 7 (3)^{2} - 15 = 7 \times 9 - 15 = 63 - 15 = 48$
And $f (5) = 7 (5)^{2} - 15 = 7 \times 25 - 15 = 175 - 15 = 160$
So, $f (3) - f (5) = 48 - 160 = - 112$

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