来自郭丹丹的问题
求3^(x+2)>2和log1/2(x-2)
求3^(x+2)>2和log1/2(x-2)
1回答
2020-11-03 04:26
求3^(x+2)>2和log1/2(x-2)
求3^(x+2)>2和log1/2(x-2)
1.因为y=3^(x+2)是增函数2边同取以3为底对数得x+2>log3(2)
所以x>log3(2)-2
2.log1/2(x-2)是减函数且log1/2(1/8)=3
所以x-2>1/8,x>2+1/8
3.2x-x^2=-(x^2-2x+1)+1=-(x-1)^2+1