A.MATHS 野

因為 如果你要搵"family of line passing though the intersection of two given lines" ge時候
(suppose the equation of 2 given lines are Ax+By+C=0 and ax+by+c=0 andthe point of inersection is (m,n) )
你出黎ge ans一定係 可以satisfy (m,n)
therefore, Ax+By+C=0 --------------(1)
ax+by+c=0 --------------(2)
(1)+(2)：點解無啦啦有個k o係度呢?
因為出黎ge ans 可以有infinity咁多嫁嗎, 只要佢係passing though the intersection of 2 given line,就可以係你ge ans

講多少少先~
通常題目都會問family of line passing though the intersection of two given lines,
佢就會比兩條式你, 你就直接寫成Ax+By+C+k(ax+by+c)=0
咁樣就拎到分嫁啦~
跟住第2part佢就會叫你搵個真正eqaution係乜,if the slope of that line is____
或者if that line also passing though ,let say, (3,2)
咁樣你就可以計條式係乜啦~

呢d題目係好好用,用黎執分@@
見到一定要做呀@@!!