解不等式log1/2(3-x)>=log2(x+3)-1

问题描述:

解不等式log1/2(3-x)>=log2(x+3)-1

Log1/2(3-x)+log1/2(1/2)≥log2(x+3)
Log1/2(3-x)+log1/2(1/2)=log1/2(3/2-x/2)=-log2(3/2-x/2)
所以-log2(3/2-x/2)≥log2(x+3)
所以log2(3/2-x/2)+log2(x+3)≤0
Log2[(3/2-x/2)×(x+3)]≤0
因为a=2>1 所以函数是增函数 所以0①0②(3/2-x/2)×(x+3)≤1 解得x≤-3或x≥3
所以x无解
结果不一定对 方法一定对
可追问 望采纳

答:
log0.5(3-x)>=log2(x+3)-1=log2[(x+3)/2]
所以:
[log2(3-x)]/[log2(1/2)]>=log2[(x+3)/2]
所以:-log2(3-x)>=log2[(x+3)/2]
所以:1/(3-x)>=(x+3)/2>0
解得:√7

log1/2 (3-x)= -log2 (3-x)
1>= log2 (3-x)(3+x)
所以: (3-x)(3+x)>0
(3-x)(3+x)解得范围(-3,-√7]并[√7,3)

log½(3-x)=-log2(3-x)≧log2(x+3)-log2(2) log2(x+3)(3-x)/2≦0 (3+X)(3-X)≦2 x≦-√7或x≧√7又因为-3《x《3
故(-3,-√7]并[√7,3)

log1/2 (3-x)≥log2 (x+3)-1-log2 (3-x)≥log2 (x+3)-log2 2log2 (3-x)+log2 (x+3)-log2 2≤0log2 [(3-x)(x+3)/2]≤log2 1因为2>1,所以log2 x为增函数0<(3-x)(x+3)/2≤10<9-x²≤27≤x²<9√7≤x<3或-3...