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E2. Change the subject of an equation In the equation y=5x-4, y is said to be the subject of the equation. In each of the following equations, the letter in red is the subject of the equation: t=4w2, x=4(y+7), w=u+½vt The subject of an equation can be changed to any of the other letters present in it by using the rules of algebra. An example Make x the subject of y=3x-8 Write down the equation    y=3x-8 Add 8 to both sides: y+8=3x Divide both sides by 3: (y+8)/3=x Thus x=(y+8)/3 Another example Make w the subject of t=2w-4 Write down the equation    t=2w - 4 Add 4 to both sides: t + 4=2w Divide both sides by 2: (t + 4)/2=w Thus w=(t + 4)/2 Yet another example Make v the subject of u=v2+7 Write down the equation u=v2+7 Subtract 7 from both sides: u-7=v2 Take the square root of both sides:  (u-7)=v Thus v=(u-7)