A) 2 2( 4) 03X X − = B) (X+2)2− −(X 2)(X+ =2) 0C) X+2 2X2+2X3 =0
81.
Tìm
x
, biết:
a)
2
2
(
4)
0
3
x x
− =
b)
(
x
+
2)
2
− −
(
x
2)(
x
+ =
2)
0
c)
x
+
2 2
x
2
+
2
x
3
=
0
.
Giải
a)
Ta có:
2
2
2
(
4)
(
2)(
2)
3
x x
− =
3
x x
−
x
+
. Do đó:
2
(
2)(
2)
0
3
x x
−
x
+
=
khi
x
=
0
,
x
=
2
hoặc
x
= −
2
.
b)
(
x
+
2)
2
− −
(
x
2)(
x
+ = +
2)
(
x
2)(
x
+ − + =
2
x
2)
4(
x
+
2)
.
Vậy
4(
x
+
2)
=
0
khi
x
= −
2
.
c)
x
(1 2 2
+
x
+
2
x
2
)
=
0
hay
x
(1 2 2 )
+
x
2
=
0
.
Vậy
x
=
0
,
1
x
= −
2
.