Quadratics - Factorising a Quadratic when "a" is equal to 1

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  • Created by: K
  • Created on: 29-10-09 22:38

Quadratics:

The standard formula for a quadratic is

ax²+bx+c=0

An example of this would be

x²+3x+2=0

Factorising quadratics when a is equal to 1

In order to solve the quadratic, you need to put it into the standard format: ax²+bx+c=0. The factorising method goes as follows:

1) ALWAYS rearrange into the STANDARD FORMAT : ax²+bx+c=0

2) Find the factors of a and c in order to factorise

3) Use the table in order to work out the factorised form of the equation.

4) Find the actual solution to the equations.

EXAMPLE:

"solve x²-x=12 by factorising"

1) Rearrange the equation into the standard format:

x²-x=12 (minus 12 from both sides)

x²-x-12=0 (now in the standard format)

2) ac= 1x-12 = -12 : we now need to find the factors of -12 and list them. The answer must multiply to make -12 and add/subtract to make b. In this case, b is equal to -1.

Factors of -12:

1 and -12

2 and -6

3 and -4

REMEMBER: Write the factors at first as if they were making positive ac (in this case 12). Then put the signs into the right side so…

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