Toán Lớp 7: Tìm x
$3^{x +2}$ + $3^{x}$=$8^{10}$
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Toán Lớp 7: Tìm x
$3^{x +2}$ + $3^{x}$=$8^{10}$
Comments ( 2 )
3
x
+
2
+
3
x
=
810
3
x
+
2
+
3
x
=
810
⇒
3
x
.3
2
+
3
x
=
810
⇒
3
x
.3
2
+
3
x
=
810
⇒
3
x
.9
+
3
x
=
810
⇒
3
x
.9
+
3
x
=
810
⇒
3
x
(
9
+
1
)
=
810
⇒
3
x
(
9
+
1
)
=
810
⇒
10.3
x
=
810
⇒
10.3
x
=
810
⇒
3
x
=
810
10
=
81
⇒
3
x
=
810
10
=
81
⇒
3
x
=
3
4
⇒
3
x
=
3
4
⇒
x
=
4
⇒
x
=
4
Vậy
x
=
4