1) y=log0,8(x2−5x+7)
log0,8(x2−5x+7)≥0
0<x2−5x+7≤1.
x2−5x+7>0
D=25−28=−3<0
x∈R.
x2−5x+7≤1
x2−5x+6≤0
D=25−24=1
x1=5−12=2;
x2=5+12=3;
(x−2)(x−3)≤0
2≤x≤3.
ОтветОтвет: x∈[2; 3].
2) y=log0,5(x2−9)
log0,5(x2−9)≥0
0<x2−9≤1.
1) x2−9>0
(x+3)(x−3)>0
x<−3; x>3.
2) x2−9≤1
x2−10≤0
(x+10)(x−10)≤0
−10≤x≤10.
ОтветОтвет:
x∈[−10; −3)∪(3; 10].
3) y=log4(1+6x)+|log18(1+7x)|
log4(1+6x)+|log18(1+7x)|≥0
log21+6x+|log21+7x3|≥0.
log21+7x3≤0
0<1+7x3≤1
0<1+7x≤1
−1<7x≤0
−17<x≤0.
−17<x≤0:
log21+6x−log21+7x3≥0
1+6x1+7x3≥1
1+6x≥1+7x3
(1+6x)3≥(1+7x)2
216x3+108x2+18x+1≥1+14x+49x2
216x3+59x2+4x≥0
x(216x2+59x+4)≥0
D=3481−3456=25
x1=−59−52∙216=−427;
x2=−59+52∙216=−18;
(x+427)(x+18)x≥0
−427≤x≤−18; x≥0.
x≥0:
log21+6x+log21+7x3≥0
1+6x∙1+7x3≥1
(1+6x)3∙(1+7x)2≥1
x∈(−17; −18]∪[0; +∞).
4) y=|log27(1+72x)|−log13(1+2x)
|log27(1+72x)|−log13(1+2x)≥0
|log31+3,5x3|+log3(1+2x)≥0.
log31+3,5x3≤0
0<1+3,5x3≤1
0<1+3,5x≤1
−1<3,5x≤0
−27<x≤0.
−27<x≤0:
−log31+3,5x3+log3(1+2x)≥0;
1+2x1+3,5x3≥1;
1+2x≥1+3,5x3
(1+2x)3≥1+3,5x
8x3+12x2+6x+1≥1+3,5x
8x3+12x2+2,5x≥0
12x(16x2+24x+5)≥0
D=576−320=256
x1=−24−162∙16=−54;
x2=−24+162∙16=−14;
(x+54)(x+14)x≥0
−55≤x≤−14; x≥0.
log31+3,5x3+log3(1+2x)≥0
1+3,5x3∙(1+2x)≥1
(1+3,5x)∙(1+2x)3≥1
x∈(−27; −14]∪[0; +∞).