maths question

Given x^2+(k-6)x-(2-k)=1 has real roots

Hence △=b^2-4ac greater than or equal to 0
(k-6)^2-4(1)(-(3-k)) greater than or equal to 0
k^2-12k+36+12-4k greater than or equal to 0
k^2-16k+48 greater than or equal to 0
(k-4)(k-12) greater than or equal to 0
So k smaller than or equal to 4 or k greater than or equal to 12

1. 我想問"greater than or equal to"點解會轉左"smaller than or equal"??
2. 同埋幾時先要咁轉??