Question

Hello people ~

factorise: 21x² - 55x + 14​​

Answer 1

Use mid term splitation

`\\ \rm\rightarrowtail 21x^2-55x+14`

`\\ \rm\rightarrowtail 21x^2-49x-6x+14`

`\\ \rm\rightarrowtail 7x(3x-7)-2(3x-7)`

`\\ \rm\rightarrowtail (7x-2)(3x-7)`

Done!

Answer 2

Explanation:

Note the x^2 term, 21 can be divided up into 1,3,7,21

and the constant term, 14 is divisible by 1,2,7

Also, note that -55 = -7*7 - 2*3

Break up 21x^2 into 7x*3x and -55x into -49x - 6x,

21x^2 - 55x + 14

= ((7x*3x) - 49x) - 6x + 14

= 7x*(3x - 7) - 2*(3x -7)

= (7x - 2)*(3x - 7)