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\(a,x+\frac{1}{2}=\frac{3}{4}.\frac{8}{6}\)
\(x+\frac{1}{2}=1\)
\(x=\frac{1}{2}\)
\(b,x-\left(\frac{1}{6}+\frac{1}{3}\right)=\frac{5}{2}.\frac{7}{5}\)
\(x-\frac{1}{6}-\frac{1}{3}=\frac{7}{2}\)
\(x-\frac{1}{6}=\frac{23}{6}\)
\(x=4\)
a, \(x^{15}=x\)
\(\Rightarrow\orbr{\begin{cases}x=1\\x=0\end{cases}}\)
b, \(\left(2x+1\right)^3=125\)
\(\Rightarrow\left(2x+1\right)^3=5^3\)
\(\Rightarrow\) \(2x+1=5\)
\(\Rightarrow\) \(2x=5-1\)
\(\Rightarrow\) \(2x=4\)
\(\Rightarrow\) \(x=4:2\)
\(\Rightarrow\) \(x=2\)
c, \(\left(x-5\right)^4=\left(x+5\right)^6\)
\(\Rightarrow\orbr{\begin{cases}x-5=0\\x-5=1\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=5\\x=6\end{cases}}\)
s1=1+2+3+...+99
s1=99+98+...+1
2s1=100+100+....+100
2s1=100.99
s1=100.99:2=4950(mấy bài sau lam tương tự nha)
4+4^2+4^3+...+4^90 chia hết cho 21
=(4+4^2+4^3)+...+(4^88+4^89+4^90)
=84.1+(4^4+4^5+4^6+...+4^90)
vì 84 chia hết cho 21 suy ra tổng trên chia hét cho 21 (ĐPCM)
a) 7x-20=21
<=> 7x=41
<=> x=\(\frac{41}{7}\)
c) \(|x-5|-1=6\)
\(\Leftrightarrow|x-5|=7\)
\(\Leftrightarrow\orbr{\begin{cases}x-5=7\\x-5=-7\end{cases}\Leftrightarrow\orbr{\begin{cases}x=12\\x=-2\end{cases}}}\)
a. 7x - 20 = 21
7x = 41
x= 41/7
b. (2x + 1)^3 = 9. 9.9
(2x + 1)^3 = 9^3
2x + 1 = 9
2x = 8
x = 4
c. | x-5| -1 = 6
| x - 5 | = 7
Th1: x- 5 = 7
x = 12
Th2: x-5 = -7
x= -2
hok tốt!!!
1. thực hiện phép tính
a, 23. 15 - [ 115 - ( 12-5)2 ]
= 23 . 15 - [ 115 - 72 ]
= 8 . 15 - 66
= 120 - 66
= 54
b,132 - [ 116 - (132 - 128)2
= 132 - [ 116 - 42 )
= 132 - 100
= 32
c, [ 545 - ( 45 + 4.25 ) ] : 50 - 2000: 250 +215: 213
= [ 545 - 145 ] : 50 -8 + 22
= 400 : 50 - 8 + 4
= 8 - 8 + 4
= 4
d, [ 1104 - ( 25.8 + 40)] :9 + 316: 312
= [ 1104 - { 200+40 } ] : 9 + 34
= { 1104 - 240 ) : 9 + 81
= 864 : 9 + 81
= 177
2.tìm x bt
a, 575 - ( 6x + 70) = 445
=> 6x +70 = 575 - 445
=> 6x + 70 = 130
=> 6x = 130 - 70
=> 6x = 60
=> x = 60:6
=> x = 10
Vậy x = 10
b, 315 + (125 - x) = 435
=> 125 - x = 435-315
=> 125-x = 120
=> x = 125-120
=> x = 5
Vậy x = 5
c, (3-x).(x-3)=0
=> \(\orbr{\begin{cases}3-x=0\\x-3=0\end{cases}}\)=> \(\orbr{\begin{cases}x=3-0\\x=0+3\end{cases}}\)=> \(\orbr{\begin{cases}x=3\\x=3\end{cases}}\)
Vậy x = 3
Câu 4:
a) Ta có: \(\left|-x+8\right|\ge0\)
\(\Rightarrow A=\left|-x+8\right|-21\ge-21\)
Vậy \(MIN_A=-21\) khi x = 8
b) Ta có: \(\left|-x-17\right|+\left|y-36\right|\ge0\)
\(\Rightarrow B=\left|-x-17\right|+\left|y-36\right|+12\ge12\)
Vậy \(MIN_B=12\) khi \(x=-17;y=36\)
c) Ta có: \(-\left|2x-8\right|\le0\)
\(\Rightarrow C=-\left|2x-8\right|-35\le-35\)
Vậy \(MAX_C=-35\) khi \(x=4\)
d) Ta có: \(3\left(3x-12\right)^2\ge0\)
\(\Rightarrow D=3\left(3x-12\right)^2-37\ge-37\)
Vậy \(MIN_D=-37\) khi x = 4
e) Ta có: \(-3\left|2x+50\right|\le0\)
\(\Rightarrow E=-21-3\left|2x+50\right|\le-21\)
Vậy \(MAX_E=-21\) khi x = -25
g) \(\left(x-3\right)^2+\left|x^2-9\right|\ge0\)
\(\Rightarrow G=\left(x-3\right)^2+\left|x^2-9\right|+25\ge25\)
Vậy \(MIN_G=25\) khi x = 3
a, 7x - 20 = 71
7x = 71 + 20
7x = 91
x = 91 : 7
x = 13
b, (2x + 1)3 = 9.81
(2x + 1)3 = 729
(2x + 1)3 = 93
=> 2x + 1 = 9
=> 2x = 9 - 1
=> 2x = 8 => x = 8 : 2 = 4
c, |x - 5| - 1 = 6
=> |x - 5| = 6 + 1 = 7
\(\Rightarrow\orbr{\begin{cases}x-5=7\\x-5=-7\end{cases}}\) \(\Rightarrow\orbr{\begin{cases}x=7+5\\x=-7+5\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=12\\x=-2\end{cases}}\)
Vậy..................
a) 7x - 20 = 71
7x = 71 + 20
7x = 91
x = 91 : 7
x = 13
b) ( 2x +1 ) 3 = 9 . 81
( 2x +1 ) 3 = 729
( 2x +1 ) 3 = 93
= > 2x + 1 = 9
2x = 9 - 1
2x = 8
x = 8 : 2
x = 4
c) | x - 5 | - 1 = 6
| x - 5 | = 6 + 1
| x - 5 | = 7
= > x - 5 = 7 hoặc x - 5 = - 7
x = 7 + 5 x = -7 + 5
x = 12 x = -2
Vậy ............