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# Factorising quadratic expressions 2

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Factorising quadratics by inspection with quadratic coefficient different from 1

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### Factorising quadratic expressions 2

1. 1. Factorisation By the end of the lesson you will be able to: • Factorise quadratic expressions(trinomials) of  the form: ax2 +bx+c
2. 2. Factorise fully:
3. 3. Factorise fully:
4. 4. Let's try to factorise   Which two terms multiply to make             ? 2x2 +7x+5 (            ) (            ) 2x2 (            ) (            ) Now, to make the :5 (            ) (            ) 2x   x  2x   x  +1  +5 Let's expand: 2x2 +10x+x+5 2x2 +11x+5
5. 5. (            ) (            )2x   x  +1  +5 We have to swap around the 1 and the 5 Now, expand again: Always expand to check !!!!!!
6. 6. Factorise: 3x2 +16x+21 (            ) (            ) List the factors of 21: so it could be: (3x +7) ( x + 3)or(3x +3) ( x + 7) Expand to see which is the correct one. So 3x2 +16x+21  = (3x +7) ( x + 3)
7. 7. Let's try to factorise 3x2 +13x­10 (            ) (            ) List the factors of -10: The best way to find the correct pair is trial and improvement
8. 8. Now even worse! 4x2 ­4x­3 Which two terms multiply to make ?4x2 It could be: or(4x     )  ( x         )  (2x      )   ( 2x       ) List the factors of -3: Now try the different possibilities until you find the correct one
9. 9. Factorise: 4x2  ­25
10. 10. solve worksheet "Factorisation " Ex D2
11. 11. 2 x3  ­ 11 x2  + 5x= At the end of the lesson: Factorise: