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Math Help - gr. 11 math question

  1. #1
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    gr. 11 math question

    gr. 11 math questions

    a cameras focal lengt, f, is relatedto the distance from the subject, s, and the image distance, i ,by the equation 1/s + 1/i = 1/f. find a formula to express f in terms of s and i.

    i have no idea watsoever wat to do
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  2. #2
    Super Member 11rdc11's Avatar
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    If I understand your question correctly it wants you to solve for f

    f= \frac{is}{i + s}
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  3. #3
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    huh how did u get that?? can u tell me how u got 2 i's and s's
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  4. #4
    Super Member 11rdc11's Avatar
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    \frac{1}{s} + \frac{1}{i}= \frac{1}{f}

    \frac{i + s}{is} = \frac{1}{f}

    is = f(i + s)

    \frac{is}{i + s} = f
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  5. #5
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    i still dun understand how they become 2 im so dumb
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  6. #6
    Super Member 11rdc11's Avatar
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    Find common denominator

    \frac{1}{s} + \frac{1}{i}

    so multiply the denominators together to find the common denominator

    \frac{(1)(i) + (1)(s)}{is}
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