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\(2.3^x+5.3^x.3=153\Leftrightarrow2.3^x+15.3^x=153\)
\(\Leftrightarrow17.3^x=153\Leftrightarrow3^x=9\Leftrightarrow x=2\)
\(\Leftrightarrow2.3^x+5.3.3^x=153\)
\(\Leftrightarrow17.3^x=3^2.17\)
\(\Leftrightarrow3^x=3^2\Rightarrow x=2\)
Ta có: \(4.3^{x+2}-2.3^{x+1}=810\)
\(4.3^{x+1}.3-2.3^{x+1}=810\)
\(2.3^{x+1}\left(2.3-1\right)=810\)
\(2.3^{x+1}.5=810\)
\(3^{x+1}=81=3^4\)
x+1=4
x=3
\(2.3^{x+1}=10.3^{12}+8.3^{12}\\ VP=\left(10+8\right).3^{12}=18.3^{12}=2.3^2.3^{12}\\ =2.3^{2+12}=2.3^{14}\\ VT=VP\\ \Rightarrow2.3^{x+1}=2.3^{14}\\ \Rightarrow x+1=14\\ Vậy:x=14-1=13\)
\(2\cdot3^{x+1}=10\cdot3^{12}+8\cdot3^{12}\\\Rightarrow 2\cdot3^{x+1}=3^{12}\cdot(10+8)\\\Rightarrow 2\cdot3^{x+1}=3^{12}\cdot18\\\Rightarrow 2\cdot3^{x+1}=3^{12}\cdot3^2\cdot2\\\Rightarrow 3^{x+1}=3^{12}\cdot3^2\\\Rightarrow 3^{x+1}=3^{14}\\\Rightarrow x+1=14\\\Rightarrow x=14-1\\\Rightarrow x=13\\Vậy:x=13\)
-1/2.3x+3/4=-2.25
-1/2.3x+3/4=9/4
-1/2.3x =9/4-3/4
-1/2.3x =3/2
3x =3/2:-1/2
3x =-3
x =-3:3
x =-1
vậy x=-1
\(-\frac{1}{2}.3x+\frac{3}{4}=-2,25\)
\(\Rightarrow\frac{1}{2}.(-3).x+\frac{1}{2}.\frac{3}{2}=\frac{9}{4}\)
\(\Rightarrow\frac{1}{2}.\left(-3x+\frac{3}{2}\right)=\frac{9}{4}\)
\(\Rightarrow-3x+\frac{3}{2}=\frac{9}{4}:\frac{1}{2}\)
\(\Rightarrow-3x+\frac{3}{2}=\frac{9}{2}\)
\(\Rightarrow-3x=3\)
\(\Rightarrow x=-1\)
\(2\cdot3^x-1=53\\ \Leftrightarrow2\cdot3^x=54\\ \Leftrightarrow3^x=27\\ \Leftrightarrow x=3\)
3.4x-2+4x-1+4x=92
4x(3+1+1)-2-1=92
4x.5-2-1=92
4x.5 =92+1+2
4x.5 =95
4x =95:5
4x =19
3.4x-2+4x-1+4x=92
4x(3+1+1)-2-1=92
4x.5-2-1=92
4x.5 =92+1+2
4x.5 =95
4x =95:5
4x =19
đây em nhé
a)7.2x=56⇔2x=8⇔2x=23⇔x=3
b)(2x+1)3=9.81⇔(2x+1)3=93⇔2x+1=9⇔2x=8⇔x=4
c)x3=82⇔x3=26⇔x=22⇔x=4
d)4.2x-3=1⇔4.2x=4⇔2x=1⇔2x=20⇔x=0
e)2.3x=162⇔3x=81⇔3x=34⇔x=4
Nguyễn Thị Mai:
\(^{\frac{1}{2.3}x+\frac{1}{3.4}x+....+\frac{1}{49.50}x=1}\)
Đặt: \(^{\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\right)x=1}\)
\(^{\Leftrightarrow\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\right)x=1}\)
\(^{\Leftrightarrow\frac{1}{2}+\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{1}{4}-\frac{1}{4}\right)+...+\left(\frac{1}{49}-\frac{1}{49}\right)-\frac{1}{50}x=1}\)
\(^{\Leftrightarrow\left(\frac{1}{2}+0+0+...+0-\frac{1}{50}\right)x=1}\)
\(^{\Leftrightarrow\left(\frac{1}{2}-\frac{1}{50}\right)x=1}\)
\(^{\Leftrightarrow\frac{12}{25}x=1}\)
\(^{\Leftrightarrow x=\frac{25}{12}}\)
Tham khảo nha ~~