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a) \(3^{x+1}-3^x=162\)
\(\Leftrightarrow3^x.\left(3-1\right)=162\)
\(\Leftrightarrow3^x.2=162\)
\(\Leftrightarrow3^x=162:2=81\)
\(\Leftrightarrow3^x=3^4\)
\(\Leftrightarrow x=4\)
b) \(\left(1-x\right)^3=216\)
\(\Leftrightarrow\left(1-x\right)^3=6^3\)
\(\Leftrightarrow1-x=6\)
\(\Leftrightarrow x=1-6\)
\(\Leftrightarrow x=-5\)
c) \(5^{x+1}-2.5^x=375\)
\(\Leftrightarrow5^x.\left(5-2\right)=375\)
\(\Leftrightarrow5^x.3=375\)
\(\Leftrightarrow5^x=375:3=125\)
\(\Leftrightarrow5^x=5^3\)
\(\Leftrightarrow x=3\)
d) \(\left(2x+1\right)^3=-64\)
=> \(\left(2x+1\right)^3=\left(-4\right)^3\)
=> \(2x+1=-4\)
=> \(2x=\left(-4\right)-1\)
=> \(2x=-5\)
=> \(x=\left(-5\right):2\)
=> \(x=-\frac{5}{2}\)
Vậy \(x=-\frac{5}{2}.\)
Mình chỉ làm câu d) thôi nhé.
Chúc bạn học tốt!
Gửi bạn Velvet Red ! Hơi bận nên chỉ làm hai phần a,b cho bạn thôi nhé !!
a) \(3^{x+2}-3^{x+1}=162\)
\(\Leftrightarrow3^x.3^2-3^x.3=162\)
\(\Leftrightarrow3^x.\left(3^2-3\right)=162\)
\(\Leftrightarrow3^x=162:6\)
\(\Leftrightarrow3^x=27=3^3\)
\(\Leftrightarrow x=3\)
Vậy : \(x=3\)
b) \(5^{x+2}-2.5^{x+1}=375\)
\(\Leftrightarrow5^x.5^2-2.5^x.5=375\)
\(\Leftrightarrow5^x.\left(5^2-2.5\right)=375\)
\(\Leftrightarrow5^x=375:15\)
\(\Leftrightarrow5^x=25=5^2\)
\(\Leftrightarrow x=2\)
Vậy : \(x=2\)
\(a)3^{x+1}-3^x=162\)
\(\Leftrightarrow3^x\cdot3-3^x=162\)
\(\Leftrightarrow3^x\left(3-1\right)=162\)
\(\Leftrightarrow3x\cdot2=162\)
\(\Leftrightarrow3x=162:2\)
\(\Leftrightarrow3x=81\)
\(\Leftrightarrow x=81:3\)
\(\Leftrightarrow x=27\)
Vậy x=27
\(b)\left(1-x\right)^3=216\)
\(\Leftrightarrow\left(1-x\right)^3=6^3\)
\(\Leftrightarrow x-1=6\)
\(\Leftrightarrow x=6+1\)
\(\Leftrightarrow x=7\)
Vậy x=7
\(c)5^{x+1}-2\cdot5^x=375\)
\(\Leftrightarrow5^x\cdot5-2\cdot5^x=375\)
\(\Leftrightarrow5^x\cdot\left(5-2\right)=375\)
\(\Leftrightarrow5^x\cdot3=375\)
\(\Leftrightarrow5^x=375:3\)
\(\Leftrightarrow5^x=125\)
\(\Leftrightarrow5^x=5^3\)
\(\Leftrightarrow x=3\)
Vậy x=3
(3x+1)^3=-216=(-6)^3
=>3x+1=-6
=>x=...
3^x-1+5.3^x-1=162
=>3^x-1.(1+5)=162
=>3^x-1.6=162
=>3^x-1=162:6=27
=>3^x-1=3^3
=>x-1=3
=>x=4
1a) \(\left|\frac{3}{2}x+\frac{1}{2}\right|=\left|4x-1\right|\)
=> \(\orbr{\begin{cases}\frac{3}{2}x+\frac{1}{2}=4x-1\\\frac{3}{2}x+\frac{1}{2}=1-4x\end{cases}}\)
=> \(\orbr{\begin{cases}-\frac{5}{2}x=-\frac{3}{2}\\\frac{11}{2}x=\frac{1}{2}\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{5}{3}\\x=\frac{1}{11}\end{cases}}\)
b) \(\left|\frac{5}{4}x-\frac{7}{2}\right|-\left|\frac{5}{8}x+\frac{3}{5}\right|=0\)
=>\(\left|\frac{5}{4}x-\frac{7}{2}\right|=\left|\frac{5}{8}x+\frac{3}{5}\right|\)
=> \(\orbr{\begin{cases}\frac{5}{4}x-\frac{7}{2}=\frac{5}{8}x+\frac{3}{5}\\\frac{5}{4}x-\frac{7}{2}=-\frac{5}{8}x-\frac{3}{5}\end{cases}}\)
=> \(\orbr{\begin{cases}\frac{5}{8}x=\frac{41}{10}\\\frac{15}{8}x=\frac{29}{10}\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{164}{25}\\x=\frac{116}{75}\end{cases}}\)
c) TT
a, \(\left|\frac{3}{2}x+\frac{1}{2}\right|=\left|4x-1\right|\)
=> \(\orbr{\begin{cases}\frac{3}{2}x+\frac{1}{2}=4x-1\\-\frac{3}{2}x-\frac{1}{2}=4x-1\end{cases}}\)
=> \(\orbr{\begin{cases}\frac{3}{2}x+\frac{1}{2}-4x=-1\\-\frac{3}{2}x-\frac{1}{2}-4x=-1\end{cases}}\)
=> \(\orbr{\begin{cases}x=\frac{3}{5}\\x=\frac{1}{11}\end{cases}}\)
\(b,\left|\frac{5}{4}x-\frac{7}{2}\right|-\left|\frac{5}{8}x+\frac{3}{5}\right|=0\)
=> \(\left|\frac{5}{4}x-\frac{7}{2}\right|-0=\left|\frac{5}{8}x+\frac{3}{5}\right|\)
=> \(\frac{\left|5x-14\right|}{4}=\frac{\left|25x+24\right|}{40}\)
=> \(\frac{10(\left|5x-14\right|)}{40}=\frac{\left|25x+24\right|}{40}\)
=> \(\left|50x-140\right|=\left|25x+24\right|\)
=> \(\orbr{\begin{cases}50x-140=25x+24\\-50x+140=25x+24\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{164}{25}\\x=\frac{116}{75}\end{cases}}\)
c, \(\left|\frac{7}{5}x+\frac{2}{3}\right|=\left|\frac{4}{3}x-\frac{1}{4}\right|\)
=> \(\orbr{\begin{cases}\frac{7}{5}x+\frac{2}{3}=\frac{4}{3}x-\frac{1}{4}\\-\frac{7}{5}x-\frac{2}{3}=\frac{4}{3}x-\frac{1}{4}\end{cases}}\)
=> \(\orbr{\begin{cases}x=-\frac{55}{4}\\x=-\frac{25}{164}\end{cases}}\)
Bài 2 : a. |2x - 5| = x + 1
TH1 : 2x - 5 = x + 1
=> 2x - 5 - x = 1
=> 2x - x - 5 = 1
=> 2x - x = 6
=> x = 6
TH2 : -2x + 5 = x + 1
=> -2x + 5 - x = 1
=> -2x - x + 5 = 1
=> -3x = -4
=> x = 4/3
Ba bài còn lại tương tự
a: \(A\left(x\right)+B\left(x\right)\)
\(=-2x^3+11x^2-5x-\dfrac{1}{5}+2x^3-3x^2-7x+\dfrac{1}{5}\)
\(=8x^2-12x\)
b: C(x)=A(x)-B(x)
\(=-2x^3+11x^2-5x-\dfrac{1}{5}-2x^3+3x^2+7x-\dfrac{1}{5}\)
\(=-4x^3+14x^2+2x-\dfrac{2}{5}\)
a) 3x-1(1+5)=162
3x-1.6=162
3x-1=162:6=27=33
=>x-1=3
x=4
b) x(x+3)=0
=>x=0 hoặc x+3=0
=>x=0 hoặc x=-3
c) Vì tích nhỏ hơn 0 nên có 1 thừa số dương và 1 thừa số âm
Có x-1>x-3
=>x-1>0 và x-3<0
=>x>1 và x<3
Vậy x=2
a) 3x-1 + 5. 3x-1 = 162
1. 3x-1 + 5. 3x-1 = 162
( 1 + 5 ) . 3x-1 = 162
6. 3x-1 = 162
3x-1 = 162 : 6
3x-1 = 27
3x-1 = 33
x - 1 =3
x = 3 + 1
x = 4
\(\frac{1}{3}.3^n+5.3^{n-1}=162\)
<=> \(3^{n-1}+5.3^{n-1}=162\)
<=> \(3^{n-1}\left(1+5\right)=162\)
<=> \(3^{n-1}.6=162\)
<=> \(3^{n-1}=162:6\)
<=> \(3^{n-1}=27\)
<=> \(3^{n-1}=3^3\)
<=> n - 1 = 3
<=> n = 3 + 1 = 4
Câu 1
a) Từ gt=>\(\hept{\begin{cases}x-5=1-3x\\x-5=3x-1\end{cases}}\)
<=>\(\hept{\begin{cases}4x=6\\2x=-4\end{cases}}\)
<=>\(\hept{\begin{cases}x=\frac{3}{2}\\x=-2\end{cases}}\)
b) Ta có: \(\hept{\begin{cases}\left(3x-1\right)^{100}\ge0,\forall x\in R\\\left(2y+1\right)^{200}\ge0,\forall x\in R\end{cases}}\)
Kết hợp với đề bài => \(\hept{\begin{cases}3x-1=0\\2y+1=0\end{cases}}\)
=>\(\hept{\begin{cases}x=\frac{1}{3}\\y=-\frac{1}{2}\end{cases}}\)
Bài 2
\(\frac{1}{3}.3^n+5.3^{n-1}=162\)
<=>\(3^{n-1}+5.3^{n-1}=162\)
<=>\(6.3^{n-1}=162\)
<=>\(3^{n-1}=27=3^3\)
<=>\(n-1=3\)
<=>\(n=4\)
b) | 3x - 4 | + | 5y + 5 | = 0
Ta có \(\hept{\begin{cases}\left|3x-4\right|\ge0\\\left|5y+5\right|\ge0\end{cases}\forall xy}\)
\(\Leftrightarrow\left|3x-4\right|+\left|5y+5\right|\ge0\forall xy\)
Do đó để tổng | 3x - 4 | + | 5y + 5 | = 0 thì \(\hept{\begin{cases}\left|3x-4\right|=0\\\left|5y+5\right|=0\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}3x-4=0\\5y+5=0\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}3x=4\\5y=-5\end{cases}}\)
\(\Leftrightarrow\hept{\begin{cases}x=\frac{4}{3}\\y=-1\end{cases}}\)
Vậy \(x=\frac{4}{3}\) và y= - 1
c) | x + 3 | + | x + 1 | = 3x (*1)
Ta có \(\hept{\begin{cases}\left|x+3\right|\ge0\\\left|x+1\right|\ge0\end{cases}\forall x}\)
\(\Leftrightarrow\) | x + 3 | + | x + 1 | \(\ge0\forall\)x
\(\Leftrightarrow3x\ge0\forall x\)
\(\Leftrightarrow x\ge0\)
\(\Leftrightarrow x+3>x+1>x\ge0\)
\(\Leftrightarrow\hept{\begin{cases}\left|x+3\right|=x+3\\\left|x+1\right|=x+1\end{cases}}\)
\(\Leftrightarrow\left|x+3\right|+\left|x+1\right|=x+3+x+1\)
\(\Leftrightarrow\left|x+3\right|+\left|x+1\right|=2x+4\) (*2)
Từ (*1) và (*2) <=> 2x + 4 = 3x
\(\Leftrightarrow4=3x-2x\)
\(\Leftrightarrow x=4\)
Vậy x = 4
Câu a t đang nghi sai đề
Lát t lm đc thì lm sau nhé
a)\(\left(1-x\right)^3=216\)
\(\Rightarrow1-x=6\)
\(\Rightarrow x=-5\)
b)\(3^{x+1}-3^x=162\)
\(\Rightarrow3^x\left(3-1\right)=162\)
\(\Rightarrow3^x=81\)
\(\Rightarrow3^x=3^4\)
\(\Rightarrow x=4\)
c)\(5^{x+1}-2.5^x=375\)
\(\Rightarrow5^x\left(5-2\right)=375\)
\(\Rightarrow5^x.3=375\)
\(\Rightarrow5^x=125\)
\(\Rightarrow5^x=5^3\)
\(\Rightarrow x=3\)
a) x=-5