S2 Maths

3x - 4y + 60 = 0

Sub A(x,0)into the equation

3(x) - 4(0) + 60 = 0

3x + 60 = 0

3x = -60

x = -20

Therefore A is (-20,0)

Sub B(0,y)into the equation

3(0) - 4(y) + 60 = 0

-4y + 60 = 0

-4y = -60

4y = 60

y = 15

Therefore B is (0,15)

Hope I can help you !!!!!

When the line cuts x-asis at point A, then
y = 0
3x - 4(0) + 60 = 0
3x = -60
x = -20

Ans: The coordinates of point A is (-20, 0)

When the line cuts y-asis at point B, then
x = 0
3(0) - 4y + 60 = 0
4y = 60
y = 15

Ans: The coordinates of point B is (0, 15)

比起單單知道答案，明白方法可能對你更有幫助

首先看到Linear Equations這個字，就知道3x - 4y + 60 = 0是一條直線 (廢話...)

看一看問題，它問的是coordinates of A and B，而問題提示x - 4y + 60 = 0 cuts the x-axis and y-axis at points A and B respectively

也就是說 A在x-axis上，B在 y-axis上

∴The coordinate of A is (a , 0)
and the coordinate of B is (0 , b)

(*注a、b是未知數，可以自己隨意假設)

現在，只要把x = a, y = 0 放進 x - 4y + 60 = 0 就可以找到 A: (a , 0) 是什麼
同樣，把x = 0, y = b 放進 x - 4y + 60 = 0 就可以知道 B: (0 , b) 是什麼

Put x=a, y=0 into x - 4y + 60 = 0 ,

a - 4(0) + 60 = 0

a = -60

∴The coordinate of A is (-60,0)

Put x=0, y=b into the equation,

(0) - 4(b) + 60 = 0

4b = 60

b = 15

∴The coordinate of B is (0,15)


可惜現在不能改變文字顏色，不然可以畫出重點部分...
還是不明白的話請留言，我看到會盡力解釋 (盡力吧...)