两边乘(x-7)(x+7)
3(x+7)+2a(x-7)=0
增根就使公分母为0
(x-7)(x+7)=0
x=7,x=-7
x=7,代入3(x+7)+2a(x-7)=0,42+0=0,不成立
x=-7,代入3(x+7)+2a(x-7)=0,0-28a=0,a=0
所以a=0
两边乘(x-7)(x+7)
3(x+7)+2a(x-7)=0
增根就使公分母为0
(x-7)(x+7)=0
x=7,x=-7
x=7,代入3(x+7)+2a(x-7)=0,42+0=0,不成立
x=-7,代入3(x+7)+2a(x-7)=0,0-28a=0,a=0
所以a=0