Question

log3(x-1)=log9(x+5)怎么解?

Answer 1

log9(x+5)=log(3)^2(x+5)=1/2log3(x+5)=log3√(x+5)

log3(x-1)=log3√(x+5)

x-1=√(x+5)

x^2-2x+1=x+5

x^2-3x-4=0

(x-4)(x+1)=0

x1=4,x2=-1

经检验得x2=-1不符合,舍去

x=4