Academic Skills Advice Linear Equations Summary Solving Linear Equations: When solving a linear equation you are trying to find the value of the letter in the equation. To do this you need to make the letter the subject of the equation. Example: Solve the equation: 6(2𝑄 + 13) = −9(𝑄 + 3) (Do this by collecting 𝑄’s at one side and numbers at the other.) Starting Equation: Multiply out the brackets: Take 78 from each side: Tidy up: Add 9Q to each side: Tidy up: 6(2𝑄 + 13) 12𝑄 + 78 12𝑄 + 78 − 78 12𝑄 12𝑄 + 9𝑄 21𝑄 = = = = = = −9(𝑄 + 3) −9𝑄 − 27 −9𝑄 − 27 − 78 −9𝑄 − 105 −9𝑄 − 105 + 9𝑄 −105 Divide each side by 21 to leave ‘Q’ on its own: 21𝑄 21 = −105 21 Simplify and tidy up: 𝑄 = −5 A quick method: When something crosses to the other side of the equals sign it does the opposite. E.g. + becomes -, x becomes ÷ and vice versa. Example: Solve the equation: 5(3𝑘 + 4) − 3(4𝑘 − 5) = 41 Starting Equation: Multiply out the brackets Collect like terms (k’s and numbers): +35 crosses the “=” sign and becomes -35: Tidy up: 3 crosses the “=” sign and divides Tidy up: © H Jackson 2011/2014 / Academic Skills 5(3𝑘 + 4) − 3(4𝑘 − 5) 15𝑘 + 20– 12𝑘 + 15 3𝑘 + 35 3𝑘 3𝑘 𝑘 = = = = = = 𝑘 = 41 41 41 41 − 35 6 6 3 2 1