EKSPONENCIJALNE i LOGARITAMSKE FUNKCIJE
PDF- ogledni primjerci - MIM-Sraga
PDF- ogledni primjerci - MIM-Sraga
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LOGARITMI kompletna rješenja<br />
www.mim-sraga.com<br />
9.<br />
( x+ ) + ( x− ) = ( x−<br />
)<br />
log ⎡⎣( x+ 2)( x− 4) ⎤⎦<br />
= log ( 2x−3)<br />
( x+ 2)( x− 4)<br />
= 2x−3<br />
1) log 2 log 4 log 2 3<br />
2<br />
x x x x<br />
x<br />
x<br />
x<br />
x<br />
2<br />
1,2<br />
− 4 + 2 −8− 2 + 3 = 0<br />
−4x− 5 = 0<br />
2<br />
( ) ( ) ( )<br />
− − 4 ± −4 −4 ⋅1⋅ − 5 4± 16+ 20 4±<br />
36 4±<br />
6<br />
= = = =<br />
2 ⋅ 1 2 2 2<br />
4− 6 2 4+<br />
6 10<br />
= = − x = =<br />
2 2 2 2<br />
=− 1 x = 5<br />
1 2<br />
1 2<br />
uvjet kaže da mora biti:<br />
x > 4<br />
x =<br />
uvjeti :<br />
pa je jedino rješenje 5<br />
x+ 2> 0 x− 4> 0 2x−3><br />
0<br />
x>− 2 x> 4 2x><br />
3<br />
⇓<br />
x > 4<br />
x ><br />
3<br />
2<br />
<br />
( x+ ) + ( x− ) = ( x+<br />
)<br />
log ⎡⎣( x+ 3) ⋅ ( x− 1) ⎤⎦<br />
= log ( 5x+<br />
7)<br />
( x+ 3) ⋅ ( x− 1)<br />
= 5x+<br />
7<br />
2) log 3 log 1 log 5 7<br />
2<br />
x x x x<br />
x<br />
x<br />
x<br />
x<br />
2<br />
1,2<br />
− + 3 −3−5 − 7 = 0<br />
−3x− 10 = 0<br />
2<br />
( ) ( ) ( )<br />
− − 3 ± −3 −4 ⋅1⋅ − 10 3± 9+ 40 3±<br />
49 3±<br />
7<br />
= = = =<br />
2 ⋅ 1 2 2 2<br />
3− 7 4 3+<br />
7 10<br />
= = − x = =<br />
2 2 2 2<br />
=− 2 x = 5<br />
1 2<br />
1 2<br />
uvjeti:<br />
x + 3 > 0 x − 1 > 0 5x<br />
+ 7 > 0<br />
x >− 3 x > 1 5x<br />
>−7<br />
⇓<br />
uvijet je x > 1<br />
x >−<br />
<br />
7<br />
5<br />
uvjet kaže da mora biti:<br />
pa je:<br />
⇓<br />
x = 5<br />
x > 1<br />
jedino rješenje<br />
21<br />
Autor zadataka: Mladen Sraga