聯立二元一次方程...

a. x=4,y=4
試下代番入去
y = 4x-12
4 = 4(4)-12
4=16-12
4 =4

x + 2y =12
4 + 2(4)=12
4 + 8 =12
12=12
所以x =4,y =4

b. x =2,y =5
x +2y = 12
2 +2(5) = 12
2 +10 =12
12=12

5x + y -15 =0
5(2) + 5 -15 =0
15-15 =0
0 = 0
所以 x =2 , y =5

c. x =3,y =0 5x + y -15 =0 5(3) +0 -15 =0 15 -15 =0 0=0

y =4x -12
0 =4(3) -12
0=0

所以 x=3 ,y=0

tips:做e種圖解法好簡單,睇兩條線相交ge位就係ans

驚錯就將d ans代番入條式到

希望幫到你:)

兩條線的交點就是它們的解
(a) x = 4, y = 4
(b) x = 2, y = 5
(c) x = 3, y = 0