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2.1.3 Solve for x 2.2 Make Rs the subject of the formula?

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    2^(x + 2) + 2^(x) / 4 + 2^(x) + 42

    (2^2) * (2^x) + (2^x) / 4 + (2^x) = 42

    (4 + (1/4) + 1) * 2^(x) = 42

    (5 + 1/4) * 2^(x) = 42

    (21/4) * 2^(x) = 42

    2^x = 42 * 4 / 21

    2^x = 2 * 4

    2^x = 8

    x = 3

    V = R / (R[s] + r) * V[dc]

    V / (R * V[dc]) = 1 / (R[s] + r)

    R * V[dc] / V = R[s] + r

    R * V[dc] / V  -  r  =  R[s]

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    • rotchm
      Lv 7
      3 months agoReport

      A few mistakes in his answer. Then again, one needs to be respectful and have a keen eye to see the mistakes. 

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  • 3 months ago

    V = R / (R_s + r) * V_dc

    We can multiply the numerators on the right side to simplify this:

    V = RV_dc / (R_s + r)

    Now multiply both sides by the denominator to get rid of the denominators:

    V(R_s + r) = RV_dc

    Distribute the left side:

    R_sV + rV = RV_dc

    Subtract rV from both sides:

    R_sV = RV_dc - rV

    Now divide both sides by V:

    R_s = (RV_dc - rV) / V

    We can simplify this to:

    R_s = RV_dc/V - r

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  • rotchm
    Lv 7
    3 months ago

    2.2)  Multiply by (R_s + r) each side. Divide by V each side.  Subtract r each side. 

    What do you get? Done!

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