Đáp án: a) $x=8$b)$x=y=2$ c)$x=0;-2$d)$x=4;5$ Giải thích các bước giải: a)$5.2^{x+1}.2^{-2} -2^x=384$$⇔2^{x-1}.(5-2)=384$$⇔2^{x-1}=128$$⇔x-1=7$$⇔x=8$b)$3^{x+2}.5^y=45^x$⇔$3^{x+2}.5^y=3^{2x}.5^x$⇔$\left \{ {{2+x=2x} \atop {x=y}} \right.$⇔$\left \{ {{x=2} \atop {x=y}} \right.$ ⇔$\left \{ {{x=2} \atop {y=2}} \right.$ c)$(x+1)^{x+1}=(x+1)^{x+3}$⇔$(x+1)^{x+1}((x+1)^2-1)=0$⇔ $(x+1)^2=1$⇔$x+1=1$ hoặc $x+1=-1$⇔$x=0$ hoặc $x=-2$d)$27<3^x≤243$⇔$3^3<3^x≤3^5$⇔$3<x≤5$mà x nguyên ⇒ $x=4$ hoặc $x=5$ Reply
su gửi……. a)5.2x+1.2−2−2x =3845.2x+1.2−2−2x =384 2x−1.(5−2)=384 2x−1.(5−2)=384 2x−1=128 2x−1=128 x−1=7 x−1=7 x=8 x=8 b)3x+2.5 =45x3x+2.5y =45x 3x+2.5y=32x.5x3x+2.5y=32x.5x {2+x=2xx=y{2+x=2xx=y {x=2x=y{x=2x=y {x=2y=2{x=2y=2 c)(x+1)x+1=(x+1)x+3(x+1)x+1=(x+1)x+3 (x+1)x+1((x+1)2−1)=0(x+1)x+1((x+1)2−1)=0 (x+1)2=1(x+1)2=1 x+1=1x+1=1 hoặc x+1=−1x+1=−1 x=0x=0 hoặc x=−2x=−2 d)27<3x≤24327<3x≤243 33<3x≤3533<3x≤353 <x≤53<x≤5 mà x nguyên thì x=4x=4 hoặc x=5 Reply
Đáp án:
a) $x=8$
b)$x=y=2$
c)$x=0;-2$
d)$x=4;5$
Giải thích các bước giải:
a)$5.2^{x+1}.2^{-2} -2^x=384$
$⇔2^{x-1}.(5-2)=384$
$⇔2^{x-1}=128$
$⇔x-1=7$
$⇔x=8$
b)$3^{x+2}.5^y=45^x$
⇔$3^{x+2}.5^y=3^{2x}.5^x$
⇔$\left \{ {{2+x=2x} \atop {x=y}} \right.$
⇔$\left \{ {{x=2} \atop {x=y}} \right.$
⇔$\left \{ {{x=2} \atop {y=2}} \right.$
c)$(x+1)^{x+1}=(x+1)^{x+3}$
⇔$(x+1)^{x+1}((x+1)^2-1)=0$
⇔ $(x+1)^2=1$
⇔$x+1=1$ hoặc $x+1=-1$
⇔$x=0$ hoặc $x=-2$
d)$27<3^x≤243$
⇔$3^3<3^x≤3^5$
⇔$3<x≤5$
mà x nguyên ⇒ $x=4$ hoặc $x=5$
su gửi…….
a)5.2x+1.2−2−2x
=3845.2x+1.2−2−2x
=384
2x−1.(5−2)=384
2x−1.(5−2)=384
2x−1=128
2x−1=128
x−1=7
x−1=7
x=8
x=8
b)3x+2.5
=45x3x+2.5y
=45x
3x+2.5y=32x.5x3x+2.5y=32x.5x
{2+x=2xx=y{2+x=2xx=y
{x=2x=y{x=2x=y
{x=2y=2{x=2y=2
c)(x+1)x+1=(x+1)x+3(x+1)x+1=(x+1)x+3
(x+1)x+1((x+1)2−1)=0(x+1)x+1((x+1)2−1)=0
(x+1)2=1(x+1)2=1
x+1=1x+1=1 hoặc x+1=−1x+1=−1
x=0x=0 hoặc x=−2x=−2
d)27<3x≤24327<3x≤243
33<3x≤3533<3x≤353
<x≤53<x≤5
mà x nguyên thì x=4x=4 hoặc x=5