7x+3=3x+9

7x+3=3x+9
7x+3=3x+9

7x+3=3x+9
原式=∫-dcost/(-c+cost)
=-ln|-c+cost|(c,d)
=-ln|-c+cosd|+ln|-c+cosc|
相加=6x³+(m+5)x²+x-4
不含x²则系数为0
m+5=0
m=-5
选B

7x-3x=9-3
4x=6
x=6÷4
x=1.5