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David
Lv 4
David asked in Science & MathematicsMathematics · 1 decade ago

Rearranging Equations help!?

how would you rearrange the equation 3(a+y)=by+7 making Y the subject of the equation???

show workings out

3 Answers

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  • rmm
    Lv 7
    1 decade ago
    Favorite Answer

    add spaces so that it is readable

    3(a + y) = by + 7

    multiply out the left side

    3a + 3y = by + 7

    get all y's on one side, others on the other

    3y - by = 7 - 3a

    factor out the left side

    y(3 - b) = 7 - 3a

    divide by the ()

    y = (7 - 3a) / (3 - b)

    Source(s): James - hopefully an A level math student knows to use the brackets to clarify what gets added/subtracted/multiplied/divided when and you just accidently left them off your answer. Technically, your bottom line answer is wrong.
  • Anonymous
    1 decade ago

    expand : 3a+3y = by + 7

    move the 'by' across to the left hand side

    3a + 3y - by = 7

    now you move the '3a' to the right hand side so that the terms containing 'y' are on the same side

    3y - by = 7 - 3a

    take out the common factor for the left hand side, which in this case is 'y'

    y(3 - b) = 7- 3a

    finally, move the '3-b' to the other side, remember that the '(3 - b)' is still multiplied with the 'y' so to move it across, you have to divide it by the other side, so now your left with

    y = 7 - 3a / 3 - b

    hope this helped

    Source(s): A-Level Maths Student
  • 1 decade ago

    add spaces so that it is readable

    3(a + y) = by + 7

    multiply out the left side

    3a + 3y = by + 7

    get all y's on one side, others on the other

    3y - by = 7 - 3a

    factor out the left side

    y(3 - b) = 7 - 3a

    divide by the ()

    y = (7 - 3a) / (3 - b)

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