Changing the subject: the subject appears twice

The Maths Habit

  1. Make x the subject of y = 7x + 2

    x = y − 27

  2. Make a the subject of P = 3a − 8

    a = P + 83

  3. Make k the subject of m = k5 + 1

    k = 5(m − 1)

I think of a number.
Multiply it by 3, or add 10:
the answer is the same.
What is my number?

5

Factorise: take x out

  1. ax − cx

    x(a − c)

  2. px + 2x

    x(p + 2)

  3. 5x − kx

    x(5 − k)

  4. x − tx

    x(1 − t)

Which terms contain x?

ax + b = cx + d ax and cx

Make x the subject of px + a = qx + b

every x termpx − qx=everything elseb − a
factorise: take x out
x(p − q)=b − a
divide by the bracket
x =b − ap − q

Make x the subject of tx − 2 = wx + 9

every x termtx − wx=everything else11
factorise: take x out
x(t − w)=11
divide by the bracket
x =11t − w

Make x the subject of px + a = qx + b

every x termpx − qx=everything elseb − a
factorise: take x out
x(p − q)=b − a
divide by the bracket
x =b − ap − q

Make x the subject of mx = nx + 5

every x termmx − nx=everything else5
factorise: take x out
x(m − n)=5
divide by the bracket
x =5m − n

Changing the subject: the subject appears twice worksheet, page 1

Answer sheet

  1. Make x the subject of y = x + 3x

    x = 3y − 1

  2. Make x the subject of y = 2x + 1x − 1

    x = y + 1y − 2

  1. Make x the subject of ax + 5 = bx + 9

    x = 4a − b

  2. Make x the subject of px + 2 = q − 3x

    x = q − 2p + 3

  3. Make x the subject of x + 4 = a(x − 2)

    x = 2a + 4a − 1
Exit tickets to print