倾斜角为π/4
k=tanπ/4=1
则-(2a²-7a+3)/(a²-9)=1
且a²-9≠0
-(2a-1)(a-3)/(a+3)(a-3)=1
-(2a-1)/(a+3)=1
1-2a=a+3
a=-2/3