4x + 3y + 2 = 0
等式两边乘以2得：
8x + 6y + 4 = 0
所以
d = |9 - 4|/ √(8² + 6²)
= 5/10
= 1/2
答：直线4x+3y+2=0和8x+6y+9=0的距离是1/2