7x+2 + 2 . 7x-1 = 345
345-(7x+23)=1722:6
345 - ( 7x + 23 ) = 1722 : 6
345 - (7x + 23) = 287
7x + 23 = 345 - 287
7x + 23 =58
7x = 58 - 23
7x =35
x = 35 : 7
x = 5
72.62-72.16+72.8
8.2x-1=256
3.5x-35=5.23
345-(7x+23)=1722:6
a) 72.62 - 72.16 + 72.8
= 72.36 - 72.16 + 72.8
= 72 . ( 36 - 16 + 8 )
= 72 . 28 = 2016
b) 8.2x-1 = 256
16x-1 = 162
x - 1 = 2
x = 2 + 1
x = 3
c) 3.5x - 35 = 5.23
3.5x - 35 = 40
3.5x = 40 + 35
3.5x = 75
5x = 75 : 3 = 25
5x = 52
=> x = 2
d) 345 - ( 7x + 23 ) = 1722 : 6 = 287
7x + 23 = 345 - 287
7x + 23 = 58
7x = 58 - 23 = 35
7x = 35
x = 35 : 7
x = 5
b) 2^x-1 = 256 : 8
2^x-1 = 32
ta thấy : 32 = 2^5
cơ số = cơ số
=> x - 1 = 5
x = 5 = 1
x = 6
tìm x
a)(3x-1)^2+2(3x-1)(2x+1)+(2x+1)^2=0
b)(7x+2)^2+(7x-2)^2-2(7x+2)(7x-2)=0
I don't now
sorry
...................
nha
a) \(\left(3x-1\right)^2+2\left(3x-1\right)\left(2x+1\right)+\left(2x+1\right)^2=0\)
\(\Leftrightarrow\)\(\left[\left(3x-1\right)+\left(2x-1\right)\right]^2=0\)
\(\Leftrightarrow\)\(\left(5x-2\right)^2=0\)
\(\Leftrightarrow\)\(5x-2=0\)
\(\Leftrightarrow\)\(x=\frac{2}{5}\)
Vậy...
b) \(\left(7x+2\right)^2+\left(7x-2\right)^2-2\left(7x+2\right)\left(7x-2\right)=0\)
\(\Leftrightarrow\)\(\left[\left(7x+2\right)-\left(7x-2\right)\right]^2=0\)
\(\Leftrightarrow\)\(4^2=0\) vô lí
Vậy pt vô nghiệm
7x+7x+1+7x+2+=3x19x343
\(7^x+7^{x+1}+7^{x+2}=3\cdot19\cdot343\)
\(\Leftrightarrow7^x=343\)
hay x=3
Tìm x để các phân số sau tối giản:
7x+1 /2, 7x+2 /3, 7x+3 /4, 7x+4 /5, ....., 7x+300 /301
do các phân số ở hàng số thứ 2 đã tối giản nên x=0=>7x=0 =>tổng các phân số sau đều tối giản
7x + 7x+1 + 7x+2 = 3*9*343
tìm x : (7x+3)2-(7x-1)(7x-3)=-12
\(\left(7x+3\right)^2-\left(7x-1\right)\left(7x-3\right)=-12\)
\(\Rightarrow49x^2+42x+9-\left(49x^2-21x-7x+3\right)=-12\)
\(\Rightarrow70x+18=0\) \(\Rightarrow x=-\dfrac{18}{70}=-\dfrac{9}{35}\)
giải các phương trình
a) (3x-2)(3x-1) = (3x+1)2
b) (4x-1)(x+1) = (2x-3)2
c) (5x+1)2 = (7x-3)(7x+2)
d) (4-3x)(4+3x)=(9x-3)(1-x)
e) x(x+1)(x+2)(x+3)=24
g) (7x - 2)2= (7x-3)(7x+2)
a) \(\left(3x-2\right)\left(3x-1\right)=\left(3x+1\right)^2\)
<=> \(9x^2-9x+2=9x^2+6x+1\)
<=> \(15x=1\) <=> \(x=\frac{1}{15}\)
b) \(\left(4x-1\right)\left(x+1\right)=\left(2x-3\right)^2\)
<=> \(4x^2+3x-1=4x^2-12x+9\)
<=> \(15x^2=10\) <=> \(x=\frac{2}{3}\)
c) \(\left(5x+1\right)^2=\left(7x-3\right)\left(7x+2\right)\) <=> \(25x^2+10x+1=49x^2-7x-6\)
<=> \(24x^2-17x-7=0\) <=> \(24x^2-24x+7x-7=0\)
<=> \(\left(24x+7\right)\left(x-1\right)=0\) <=> \(\orbr{\begin{cases}x=-\frac{7}{24}\\x=1\end{cases}}\)
d) (4 - 3x)(4 + 3x) = (9x - 3)(1 - x)
<=> 16 - 9x2 = 12x - 9x2 - 3
<=> 12x = 19
<=> x = 19/12
e) x(x + 1)(x + 2)(x + 3) = 24
<=> (x2 + 3x)(x2 + 3x + 2) = 24
<=> (x2 + 3x)2 + 2(x2 + 3x) - 24 = 0
<=> (x2 + 3x)2 + 6(x2 + 3x) - 4(x2 + 3x) - 24 = 0
<=> (x2 + 3x + 6)(x2 + 3x - 4) = 0
<=> \(\orbr{\begin{cases}x^2+3x+6=0\\x^2+3x-4=0\end{cases}}\)
<=> \(\orbr{\begin{cases}\left(x+\frac{3}{2}\right)^2+\frac{15}{4}=0\left(vn\right)\\\left(x+4\right)\left(x-1\right)=0\end{cases}}\)
<=> \(\orbr{\begin{cases}x=-4\\x=1\end{cases}}\)
g) (7x - 2)2 = (7x - 3)(7x + 2)
<=> 49x2 - 28x + 4 = 49x2 - 7x - 6
<=> 21x = 10 <=> x = 10/21
giải các phương trình
a) (3x-2)(3x-1) = (3x+1)2
b) (4x-1)(x+1) = (2x-3)2
c) (5x+1)2 = (7x-3)(7x+2)
d) (4-3x)(4+3x)=(9x-3)(1-x)
e) x(x+1)(x+2)(x+3)=24
g) (7x - 2)2= (7x-3)(7x+2)
7x.(1/7x-2x^2+1)
`@` `\text {Ans}`
`\downarrow`
`7x*(1/7x - 2x^2 + 1)`
`= 7x*1/7x + 7x*(-2x^2) + 7x`
`= x^2 - 14x^3 + 7x`
`= -14x^3 + x^2 + 7x`