8926655
Description
Flashcards by Liffey Farrell, updated more than 1 year ago
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Created by Liffey Farrell
about 7 years ago
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| Question | Answer |
| Solving quadratic equations by factorising: To solve a quadratic equation, the first step is to write it in the form ax2 + bx + c = 0 | If we have two numbers, A and B, and we know that A x B = 0, then it must follow that either A = 0, or B = 0 (or both). When we multiply a number by 0, we get 0. |
| Example: Solve the equation x2 - 9x + 20 = 0 | - First, factorise the quadratic equation - Find two numbers which add up to 9 and multiply to give 20. These numbers are 4 and 5. (x - 4) (x - 5) = 0 |
| Now find the value x so that when these brackets are multiplied together the answer is 0 This means either (x - 4) = 0 or (x - 5) = 0 So x = 4 or x = 5 | You can check these answering by substituting 4 and 5 into the equation: 4(2) - 9 x 4 + 20 = 16 - 36 + 20 = 0 5(2) - 9 x 5 + 20 = 25 - 45 + 20 = 0 |
| Using the quadratic formula: Here a, b and c are numbers that vary for different equations. So if the equation was 2x(2) + 7x + 11 = 0 then a = 2, b = 7 and c = 11 | The formula for the solution is: |
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