Question

Factorise a) 3x^2-7x+2 b)2x^2-x-3 c)3x^2-16x-12

Answer 1

Answer: Answers are in the steps read carefully!

Step-by-step explanation:

A) 3x^2 - 7x + 2 To factor this polynomial, you have to find two numbers that their product is 6 and their sum is -7.  The numbers -1 and -6 works out because -6 times -1 is 6  and -6 plus -1 is -7.

Now rewrite the polynomial as

3x^2 - 1x - 6x + 2   Now group it  

(3x^2 - 1x) (-6x+2)  Factor it by groups

x (3x -1)  -2(3x -1)    Now factor out 3x-1  

(3x -1) (x-2)  Done!    

B)  2x^2 - x -3     Now the same way.You will have two numbers that  their product is -6 and their sum is -1. You may be wondering how I get -6 .I get -6 by multiply the leading coefficient  2 by the constant -3.  The numbers -3 and 2 works out. Because -3 times 2 is -6 and -3 plus 2 is -1.

 Rewrite the polynomial as

2x^2 +2x - 3x -3     GRoup them and factor them

(2x^2 + 2x)  (-3x-3)  

2x(x+1) -3(x+1)  Factor out x+1

(x+1) (2x -3) Done!  

C) 3x^2 - 16x - 12   Find two numbers that their product is -36 and their sum is -12. The numbers -18 and 2 works out because -18 times 2 is -36 and -18 plus 2 is -16.

Rewrite the polynomial

3x^2 +2x -18x - 12   GRoup them

 (3x^2 + 2x)   (-18x - 12)   Factor them

x (3x +2) -6(3x +2)  Factor out 3x+2

(3x+2) (x -6)  Done !