tìm số tự nhiên x thỏa mãn
a, (2x -25) : 3 = 27
b, (x-3) . ( 8-x ) = 0
c, 889 - 5x - 2x = 375
d, 516 - ( 246 + 3x ) = 26
e, x + 1 + 2 + 3 + 4 + .....+49 + 50 = 1500
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TV
3
13 tháng 11 2021
a) \(\Leftrightarrow\left[{}\begin{matrix}2x+3=0\\5x-15=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{3}{2}\\x=3\end{matrix}\right.\)
b) \(\Leftrightarrow\left[{}\begin{matrix}3x+1=0\\3x-9=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{3}\\x=3\end{matrix}\right.\)
N
13 tháng 11 2021
a. \(\left[{}\begin{matrix}2x+3=0\\5x-15=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-3}{2}\\x=3\end{matrix}\right.\)
b. \(\left[{}\begin{matrix}3x+1=0\\3x-9=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1}{3}\\x=3\end{matrix}\right.\)
BT
2 tháng 6 2017
a) \(\dfrac{2}{3}x-\dfrac{1}{2}=\dfrac{1}{10}\)
\(\dfrac{2}{3}x=\dfrac{1}{10}+\dfrac{1}{2}=\dfrac{3}{5}\)
\(x=\dfrac{3}{5}:\dfrac{2}{3}=\dfrac{9}{10}\)
b) \(\dfrac{39}{7}:x=13\)
\(x=\dfrac{\dfrac{39}{7}}{13}=\dfrac{3}{7}\)
c) \(\left(\dfrac{14}{5}x-50\right):\dfrac{2}{3}=51\)
\(\dfrac{14}{5}x-50=51\cdot\dfrac{2}{3}=34\)
\(\dfrac{14}{5}x=34+50=84\)
\(x=\dfrac{84}{\dfrac{14}{5}}=30\)
d) \(\left(x+\dfrac{1}{2}\right)\left(\dfrac{2}{3}-2x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=0\\\dfrac{2}{3}-2x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{2}\\x=\dfrac{1}{3}\end{matrix}\right.\)
e) \(\dfrac{2}{3}x-\dfrac{1}{2}x=\dfrac{5}{12}\)
\(\dfrac{1}{6}x=\dfrac{5}{12}\)
\(x=\dfrac{5}{12}:\dfrac{1}{6}=\dfrac{5}{2}\)
g) \(\left(x\cdot\dfrac{44}{7}+\dfrac{3}{7}\right)\dfrac{11}{5}-\dfrac{3}{7}=-2\)
\(\left(x\cdot\dfrac{44}{7}+\dfrac{3}{7}\right)\cdot\dfrac{11}{5}=-2+\dfrac{3}{7}=-\dfrac{11}{7}\)
\(x\cdot\dfrac{44}{7}+\dfrac{3}{7}=-\dfrac{11}{7}:\dfrac{11}{5}=-\dfrac{5}{7}\)
\(\dfrac{44}{7}x=-\dfrac{5}{7}-\dfrac{3}{7}=-\dfrac{8}{7}\)
\(x=-\dfrac{8}{7}:\dfrac{44}{7}=-\dfrac{2}{11}\)
h) \(\dfrac{13}{4}x+\left(-\dfrac{7}{6}\right)x-\dfrac{5}{3}=\dfrac{5}{12}\)
\(\dfrac{25}{12}x-\dfrac{5}{3}=\dfrac{5}{12}\)
\(\dfrac{25}{12}x=\dfrac{5}{12}+\dfrac{5}{3}=\dfrac{25}{12}\)
\(x=1\)
Mỏi tay woa bn làm nốt nha!!
29 tháng 6 2023
6(1-x)+4(2-x)<=3(1-3x)
=>6-6x+8-4x<=3-9x
=>-10x+14<=-9x+3
=>-x<=-11
=>x>=11
(1-2x)/4-2<-5x/8
=>2-4x-16<-5x
=>-4x-14<-5x
=>x<14
Số tự nhiên x thỏa mãn cả hai BPT khi và chỉ khi 11<=x<14
=>\(x\in\left\{11;12;13\right\}\)
22 tháng 9 2020
a) ( x - 1 )2 - ( x - 1 )( x + 1 ) = 0
<=> x2 - 2x + 1 - ( x2 - 1 ) = 0
<=> x2 - 2x + 1 - x2 + 1 = 0
<=> 2 - 2x = 0
<=> 2x = 2
<=> x = 1
b) ( 2x - 1 )2 - ( 2x + 1 )2 = 0
<=> [ ( 2x - 1 ) - ( 2x + 1 ) ][ ( 2x - 1 ) + ( 2x + 1 ) ] = 0
<=> ( 2x - 1 - 2x - 1 )( 2x - 1 + 2x + 1 ) = 0
<=> -2.4x = 0
<=> -8x = 0
<=> x = 0
c) 25( x + 3 )2 + ( 1 - 5x )( 1 + 5x ) = 8
<=> 52( x + 3 )2 + 12 - 25x2 = 8
<=> [ 5( x + 3 ) ]2 + 1 - 25x2 = 8
<=> ( 5x + 15 )2 + 1 - 25x2 = 8
<=> 25x2 + 150x + 225 + 1 - 25x2 = 8
<=> 150x + 226 = 8
<=> 150x = -218
<=> x = -218/150 = -109/75
d) 9( x + 1 )2 - ( 3x - 2 )( 3x + 2 ) = 10
<=> 32( x + 1 )2 - ( 9x2 - 4 ) = 10
<=> [ 3( x + 1 ) ]2 - 9x2 + 4 = 10
<=> ( 3x + 3 )2 - 9x2 + 4 = 10
<=> 9x2 + 18x + 9 - 9x2 + 4 = 10
<=> 18x + 13 = 10
<=> 18x = -3
<=> x = -3/18 = -1/6
22 tháng 9 2020
a) (x - 1)2 - (x - 1)(x + 1) = 0
=> (x - 1)2 - (x2 - 12) = 0
=> x2 - 2.x.1 + 12 - x2 + 1 = 0
=> x2 - 2x + 1 - x2 + 1 = 0
=> -2x + 1 + 1 = 0
=> -2x + 2 = 0
=> -2x = -2 => x = 1
b) (2x - 1)2 - (2x + 1)2 = 0
=> (2x - 1 - 2x + 1)(2x - 1 + 2x + 1) = 0
=> 0 = 0(đúng)
c) 25(x + 3)2 + (1 - 5x)(1 + 5x) = 8
=> 25(x2 + 2.x.3 + 32) + (12 - (5x)2) = 8
=> 25x2 + 150x + 225 + 1 - 25x2 = 8
=> 150x +225 + 1 = 8
=> 150x = -218
=> x = -109/75
d) 9(x + 1)2 - (3x - 2)(3x + 2) = 10
=> 9(x2 + 2x + 1) - [(3x)2 - 22 ] = 10
=> 9x2 + 18x + 9 - (9x2 - 4) = 10
=> 9x2 + 18x + 9 - 9x2 + 4 = 10
=> 18x + 9 + 4 = 10
=> 18x = -3
=> x = -1/6
5 tháng 11 2017
Giải như sau.
(1)+(2)⇔x2−2x+1+√x2−2x+5=y2+√y2+4⇔(x2−2x+5)+√x2−2x+5=y2+4+√y2+4⇔√y2+4=√x2−2x+5⇒x=3y(1)+(2)⇔x2−2x+1+x2−2x+5=y2+y2+4⇔(x2−2x+5)+x2−2x+5=y2+4+y2+4⇔y2+4=x2−2x+5⇒x=3y
⇔√y2+4=√x2−2x+5⇔y2+4=x2−2x+5, chỗ này do hàm số f(x)=t2+tf(x)=t2+t đồng biến ∀t≥0∀t≥0
Công việc còn lại là của bạn !
30 tháng 9 2018
\(\left(x+6\right)\left(2x+1\right)=0\)
<=> \(\orbr{\begin{cases}x+6=0\\2x+1=0\end{cases}}\)
<=> \(\orbr{\begin{cases}x=-6\\x=-\frac{1}{2}\end{cases}}\)
Vậy....
hk tốt
^^
16 tháng 11 2021
a: \(x\in\left\{0;25\right\}\)
c: \(x\in\left\{0;5\right\}\)
a) ( 2x - 25 ) : 3 = 27
( 2x - 25 ) = 81
2x = 81 + 25
2x = 106
x = 53
b) ( x - 3 ) ( 8 - x ) = 0
\(\Rightarrow\orbr{\begin{cases}x-3=0\\8-x=0\end{cases}}\)\(\Rightarrow\orbr{\begin{cases}x=3\\x=8\end{cases}}\)
d) 516 - ( 246 + 3x ) = 26
246 + 3x = 490
3x = 244
x =
a)(2x - 25) : 3 = 27
=> 2x - 25 = 27 . 3
=> 2x - 25 = 81
=> 2x = 81 + 25 = 106
=> x = 106 : 2 = 53
b)(x - 3).(8 - x) = 0
=> x - 3 = 0 hoặc 8 - x = 0
=> x = 3 hoặc x = 8
c) 889 - 5x - 2x = 375
=>889 - 7x = 375
=>7x = 889 - 375
=>7x = 514
=>x = 514/7
d) 516 - ( 246 + 3x ) = 26
=> 246 + 3x = 516 - 26
=> 246 + 3x = 490
=> 3x = 490 - 246
=> 3x = 244
=> x = 244/3
e) x + 1 + 2 + 3 + ... + 50 = 1500
=>x + (1 + 2 + 3 + ... + 50) = 1500
=>x + 50.(50+1):2 = 1500
=>x + 1275 = 1500
=>x = 1500 - 1275
=>x = 225