1. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
EJERCICIOS RESUELTOS DE ALGEBRA
PREUNIVERSITARIA
LOGARITMOS Y ECUACIONES LOGARITMICAS
Ing. WIDMAR AGUILAR, Msc
Abril 2021
15. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
e = .F
ZF
=
WXYf
WXY.
WXYf
WXYZ
=
e =
( . )
=
%
De: 3 = g → g = →
h
=
%h
h
=
%h
h
%
→
%h
h
= e
K =
%h
h
→ (*)
73)
E=
00
F
. log L (1) ; x> 0 , x+1 > 0
= log 100 = 010
= 2 → ( )
74)
E= &P
√&
i A
√
P
=
&
2
i
jP
2
P
%A
=
&
iPj2
i
iPj2
P
16. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
=
iPj2
P
iPj2
i
=
A
B
→ (*)
75)
F]2 =x → (L) = L
= L)` ---------(1)
= F]
kF√]
`
√]
.
= F]
F
2
`.]
2
2l
]
2
.
= F]
F
2
`
]
2
.
E
2
2l
= F]
F
2
`
]
c
.l
= F]L
2
` − F]
c
.l
= F]L −
0 F]
=
fmF) fm]
0
(1)En E:
= f.f
E
`
F)
ff
E
`
F
E`
0
=
0
n 6
F
2
`
L − 7
F
2
`
L)`o
=
0
p 6. 2
`
FL − 7.
)`
2
`
FLq
=
0
r 30. FL + 7.
0
FLs
17. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
=
0
r 30 (1) + 7.
0
(1)s
= 1 +
=
76)
= 3 → = 2 − − − −( )
/ 5
F ]`
6 = 6
f m`
/
= 6 → log (
F ]`
) = 6 8
log (
F ]`
) = 8
F ]`
= 8 = 2 /
L = 2 → L (2 ) = 2
L = 2 → L = ±4
Como : = 8
|F|
]
=
/
= → (*)
23. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
9L = 0 → [0
= L → L = 1
4 93 − L = 0 → L = 4 93
4 93 > 1
L = 4 93 (€ • : •) → (H)
85)
Z ` F
+
`E2F
= ; x> 0, x≠ 1
` F
+
`E2F
=
2
` F
+
) `F
=
` F
−
`F
=
` % `F
−
`F
= →
% `F
−
`F
=
4 L − (1 + L) = (1 + L) L
4 L − 1 − L = L + ( L)
3 L − 1 = L + ( L)
L -1 = ( L)
2( L) − 7 L +3=0
L =
±√ )
=
±
L = 3 → L = 5 = 125
24. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
L = 1/2 → L = 5
2
L . L = 125. 5
2
= 5 . 5
2
L . L = 5
c
→ (H)
86)
L + E2L +
√
L + L = 10 ; x> 0
L − L + L + L = 10
L + .F
.
= 10
L + .F
= 10
2 L + .F
= 10
4 L + L = 20
5 L = 20 → L = 20
3 0
= L
3 = L
L = 81 → ( )
87)
F5.
`5
f
`
6
+
`5
f
Z `
6
= 0
29. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
92)
6 + 5 L = ( f )
; x> 0 , x ≠ 1
6 + 5 L = (
f
)
6 + 5 L = ( L)
; = L
; − 5; − 6 = 0
; =
±√ %
=
±
}
; = 6
; = −1
Luego:
L = 6 → L = 2 = 64
L = −1 → L = 2)
=
L . L = 64.
L . L = 32 → (H)
93)
log (√L + 2L + 3 = logU√L − 1
.
V)
30. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
L + 2L − 3 > 0 → L < −3 • L > 1
log(L + 2L + 3)
2
= log(L − 1)
.
.
2
.
(L + 2L + 3)
2
= (L − 1)
2
L + 2L + 3 = L − 1
(L − L )- (2x-2) = 0
L (L − 1) − 2(L − 1) = 0
(L − 1)(L − 2) = 0
}
L = 1 ó
L = 2 → L = ± √2
− √2 … … 9 *;:† [
1 -------- vuelve infinito a unos de los logaritmos,
No cumple
L = √2 → ( )
94)
√F) √L + L = 2
√F)
√L + L = 2
F) L + L = 2
(L − 7) = L + L
L − 14L + 49 = L + L
15L = 49 → L =
31. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
L = → ‡[ H[ •ˆ…: [‡ 9[ …ˆ€
Y por tanto no existe
→ 0 ‡ ;*ˆ 9[‡ → ([)
95)
|L| + L + 4 = 4 U√ FV
log L + L + 4 = √2L
log L + L + 4 = (√2L)
log L + L + 4 = 2L
log L = L − 4 ; X > 0
Graficando las ecuaciones: se ve se cortan en dos puntos
Soluciones = 2 → (*)
96)
32. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
(5
2
f + 125) = 30 +
F
(5
2
f + 125) − 30 =
F
7
2
f%
0
8 =
F
7
2
f%
0
8 = 5
2
f
2
f%
0
= 5
2
f
2
f
0
+
0
= 5
2
f
7
2
f
0
+
0
8 = 55
2
f6
(
2
f)
00
+
0.
2
f
00
+
00
= 5
2
f
55
2
f6 − 650. 5
2
f + 15625 = 0
5
2
f =
0±√ 0 ) 00
=
0± 00
5
2
f2 = 625 → 5
2
f2 = 5 →
F2
= 4
L =
5
2
f = 25 → 5
2
f = 5 →
F
= 2
L =
L + L = +
L + L = → ( )
33. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
97)
5 U ( L)V6 = 5 : x >0
U ( L)V = 5
U ( L)V = 4
( L) = 4
( L) = 1024
( L) = 3 0
L = 3 0
X = 2
2l
→ ([)
98)
(2L + 15L + 26) = 4
2L + 15L + 26 = 4
2L + 15L − 38 = 0
L =
) ±√ % 0
=
) ±
L = 2 ; L = −
L +L = 2 −
39. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
L =
±√ %
=
±
}
L = 4
L = −1
Como la base x > 0 y x≠ 1 → L = −1 9 *;:† [
L = 4
= L
= . =
= → ( )
106)
&64. F = 6 +*. -L. F
Por regla de la cadena:
&64. F = 6 +
&64. F = 6
&
.
&
F
=6
F
= 6
log 64 = 6. L
log 64 = log L
2 = L
L = 2 → 2 =
= 1 → ( )
40. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
107)
25 f = (L − 5L + 15) f ; x >0 , x ≠ 1
3 f = (L − 5L + 15) f
3 f = (L − 5L + 15) f
3 f = (L − 5L + 15) f
(3 ) f = (L − 5L + 15) f
9 f = (L − 5L + 15) f
L − 5L + 15 = 9
L − 5L + 6 = 0
L =
±√ )
=
±
}
L = 3
L = 2
=
F2.F
%F2%F
=
( )
% %
=
E = 1 → ( )
108)
9L. L + 9[. = 9L •
41. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
9L. L + = 9L •
( 9L) − 2[ 9L + = 0
3( 9L) − 6[ 9L + 4 = 0
9L =
•±√ • ) /
=
•± √ • )
9L = e ± √9[ − 12
L = [•%
2
.
√ • )
L = [•)
2
.
√ • )
L . L = [•%
2
.
√ • )
. [•)
2
.
√ • )
L . L = [•%
2
.
√ • ) %•)
2
.
√ • )
L . L = [ •
→ (H)
109)
.F
+
c 0F
+
“E2 f
2l
= 0
.F
+
.. 0F
+
.E f
2l
= 0
.F
+ 2
. . 0F
+ E2
.
f
2l
= 0
.F
+
. 0F
−
.
f
2l
= 0
.F
+
. 0% .F
−
.F) . 0
= 0
42. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
( .F) )( . 0) % .F( .F) . 0)) .F( .F% 0)
.F.(( .F) )( .F) )
= 0
2 ( L) − 5 L. 10 − ( 10) = 0
L = . 0±k ( . 0) %/( . 0)
L = . 0±k ( . 0)
L = . 0± √ . 0
L = 10 +
√
10
L = 10
`
+ 10
√..
L = (10
`
. 10
√..
)
L = 10
`
%√..
L = 10
`
− 10
√..
L = (10
`
. 10
√..
)
L = 10
`
)√..
L . L = 10
`
%√..
10
`
)√..
L . L = 10
`
%
`
= 10
`
L . L = √10 = 100√10
L . L = 100√10 → (*)
43. ALGEBRA PREUNIVERSITARIA Ing. Widmar Aguilar, Msc.
110)
L F
=
0Z
F
Tomando logaritmos de la expresión:
log (L F
) =
0Z
F
L. log L = log 10 − log L
( L) + log L = 6
( L) + log L − 6 = 0
( L + 3)( L − 2) = 0
}
log L = −3
log L = 2
log L = −3 → L = 10)
log L = 2 → L = 10
L . L = 10)
. 10 = 10)
L . L =
0
→ ([)