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Factorising

Factorising

  • Factorising is the opposite of expanding brackets

  • You need to look for the largest factors you can take out of every term in the expression

Factorising x^2 + bx + c

  • You need to write the expression with two brackets

  • x^2 + 7x + 10

    • You need to find two numbers which add up to 7 and multiply to make 10

    • 5+2=7

    • 5x2=10

    • When factorising x^2 + bx + x use this table to help find the two numbers

b

c

Factors

Positive

Positive

Both numbers positive

Positive

Negative

Bigger number positive and smaller number negative

Negative

Negative

Bigger number negative and smaller number positive

Negative

Positive

Both numbers negative

Factorising ax^2 + bx + x

  • One of the brackets must contain a ax term

  • Try pairs of numbers which have a product of c

  • Check each pair by multiplying out the brackets

Difference of two squares

  • You can factorise expression that are written as something^2 - something else^2

Factorising

Factorising

  • Factorising is the opposite of expanding brackets

  • You need to look for the largest factors you can take out of every term in the expression

Factorising x^2 + bx + c

  • You need to write the expression with two brackets

  • x^2 + 7x + 10

    • You need to find two numbers which add up to 7 and multiply to make 10

    • 5+2=7

    • 5x2=10

    • When factorising x^2 + bx + x use this table to help find the two numbers

b

c

Factors

Positive

Positive

Both numbers positive

Positive

Negative

Bigger number positive and smaller number negative

Negative

Negative

Bigger number negative and smaller number positive

Negative

Positive

Both numbers negative

Factorising ax^2 + bx + x

  • One of the brackets must contain a ax term

  • Try pairs of numbers which have a product of c

  • Check each pair by multiplying out the brackets

Difference of two squares

  • You can factorise expression that are written as something^2 - something else^2

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