Changing The SubjectChange the subject in formulae in which the new subject appears twice. 
I have made \(x\) the subject of two formulae below but there are some gaps in my working. Fill in the gaps to make the the methods correct.
InstructionsTry your best to answer the questions above. Type your answers into the boxes provided leaving no spaces. As you work through the exercise regularly click the "check" button. If you have any wrong answers, do your best to do corrections but if there is anything you don't understand, please ask your teacher for help. When you have got all of the questions correct you may want to print out this page and paste it into your exercise book. If you keep your work in an ePortfolio you could take a screen shot of your answers and paste that into your Maths file. 



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Level 1  Formulas which can be rearranged by adding or subtracting terms from both sides
Example: Make e the subject of the formula d = e  f
Level 2  Formulas which can be rearranged by multiplying or dividing both sides by a value
Example: Rearrange the formula n = mp
Level 3  Formulas which can be rearranged by adding, subtracting, multiplying or dividing both sides by a value
Example: Rearrange the formula b = a + cd
Level 4  Formulas including brackets or expressions in the numerator or denominator of a fraction
Example: Rearrange the formula p = s(t + 2)
Level 5  Formulas including squares or square roots
Example: Rearrange the formula d² = 2a + 1
Level 6  Finding the unknown which is not the subject of a formula
Example: If m = n² + 2p, find p when m=8 and n=10
Level 7  Rearrange the formulae where the new subject appears twice; fill in the blanks
Example: Rearrange the formula ax + b = cx + g to make x the subject
Level 8  Rearrange the formulae where the new subject appears twice; show your working
Example: Rearrange the formula a(3x)=5x to make x the subject
Exam Style Questions  A collection of problems in the style of GCSE or IB/Alevel exam paper questions (worked solutions are available for Transum subscribers).
More Algebra including lesson Starters, visual aids, investigations and selfmarking exercises.
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See the National Curriculum page for links to related online activities and resources.
Make \(x\) the subject of the following formula:
$$ a = \frac{bx}{2x+c} $$Multiply both sides of the equation by \(2x+c\)
$$ 2ax + ac = bx $$Add \(x\) and subtract \(ac\) from both sides
$$ 2ax + x = b  ac $$Factorise the left side
$$ x(2a + 1) = b  ac $$Divide both sides by \(2a + 1\)
$$ x= \frac{b  ac}{2a + 1} $$Don't wait until you have finished the exercise before you click on the 'Check' button. Click it often as you work through the questions to see if you are answering them correctly. You can doubleclick the 'Check' button to make it float at the bottom of your screen.
Answers to this exercise are available lower down this page when you are logged in to your Transum account. If you don’t yet have a Transum subscription one can be very quickly set up if you are a teacher, tutor or parent.
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