F4 maths 指數函數

1.若9^(x+2)=36,則3^x=?36=(3^2)^(x+2)=3^(2x+4)=3^(2x)*3^4=81*3^(2x)3^(2x)=36/813^x=√(36/81)=6/9=2/3......ans
2.若a及b均為正數,則w=1/√a^3 ÷ √b/a=w=(1/√a^3)*(a/√b)=a/(a√a*√b)=1/√(a*b)=√(a*b)/(a*b)......ans=(C)

1/.3^2(x+2)=36

3^2x(3^4)=36
3^2x=36/81
3^x=4/9



第二條是c
因為通常計到答案是1/root of ab
冇化為有理數
(1/root of ab)(root of ab/root of ab)