f/ 11x(X+2) = 5xX + 40
g/ 11x(X-6) = 4xX + 11
h/ (3xX - 4) : X + 10 = 12
k/ (5xX + 7) : X + 20 = 26
m/ Xx1999 - X = 1999x1997+1999
f/ 11x(X+2) = 5xX + 40
g/ 11x(X-6) = 4xX + 11
h/ (3xX - 4) : X + 10 = 12
k/ (5xX + 7) : X + 20 = 26
m/ Xx1999 - X = 1999x1997+1999
Đổi x thành a, ta có:
f. 11 x ( a + 2) = 5 x a + 40
11 x a + 11 x 2 = 5 x a + 40
11 x a + 22 = 5 x a + 40
6 x a + 5 x a + 22 = 5 x a + 40
6 x a + 22 = 40(Cùng bỏ 5 x a ở hai vế)
6 x a = 40 - 22
6 x a = 18
a = 18 : 6
a = 3
g. 11 x ( a - 6 ) = 4 x a + 11
11 x a - 11 x 6 = 4 x a + 11
4 x a + 7 x a - 66 = 4 x a + 11
7 x a - 66 = 11(Cùng bỏ đi 4 x a ở 2 vế)
7 x a = 11 + 66
7 x a = 77
a = 77 : 7
a = 11
h. ( 3 x a - 4 ) : a + 10 = 12
3 x a - 4 = ( 12 - 10 ) x a
3 x a - 4 = 2 x a
2 x a + a = 2 x a + 4
a = 4(Cùng bỏ đi 2 x a)
k. Tương tự h
m. a x 1999 - a = 1999 x 1997 + 1999
a x 1998 = 1999 x 1998
=> a = 1999
BÀi 7 tìm số tự nhiên x biết
d) 35 : ( 2x x + 3) - 3 = 11 - 9 x 2,5 x 0,4; 8xx+ 4xx- 44=100; 5xx+ 3xx+ 4 = 68
e) ( x+1) + ( x+2) ....... + ( x + 211) = 23632
f) (1+3+5+7+........+2009) + x = 1010026
bài 8: tính hợp lí
( 98x 7676 - 9898 x 76) : ( 2+4 +6+........+200)
e) (x + 1) + (x + 2) + .... + (x + 211) = 23632
(x + x + .... + x) + (1 + 2 + ... + 211) = 23632
211x + 22366 = 23632
211x = 23632 - 22366
211x = 1266
=> x= 6
f) (1 + 3 + 5 + 7 + .... + 2009) + x = 1010026
Số số hạng của 1 + 3 + 5 + 7 + .... + 2009 là: (2009 - 1) : 2 + 1 = 1005
Tổng của 1 + 3 + 5 +... + 2009 là: (1 + 2009) x 1005 : 2 = 1010025
Ta được : 1010025 + x = 1010026
=> x = 1010026 - 1010025 = 1
Bài 8:
( 752248-752248) : ( 2+4+6+...+200)
0 : ( 2+4+6+200)=0
Chúc bạn hok tốt nha!
11x(X-5)=5xX+11
11x(X-5)=5xX+11
11xX-55=5xX+11
11xX-5xX=11+55
6xX=66
X=66:6=11
Ta có : 11.(x - 5) = 5x + 11
=> 11x - 55 = 5x + 11
=> 11x - 5x = 11 + 55
=> 6x = 66
=> x = 66 : 6
=> x = 11
\(11\times\left(x-5\right)=5\times x+11\)
\(11x-11\times5=5x+11\)
\(11x-55=5x+11\)
\(11x-5x=11+55\)
\(6x=66\)
\(x=11\)
Xx1999-X=1999x1997+1999
x × 1999 - x = 1999 × 1997 + 1999
x × (1999 - 1) = 1999 × (1997 + 1)
x × 1998 = 1999 × 1998
=> x = 1999
Vậy x = 1999
X x 1999 - X = 1999 x 1997 + 1999
X x ( 1999 - 1 ) = 1999 x ( 1997 - 1 )
X x 1998 = 1999 x 1998
suy ra X = 1999
( 5xX+7):2= 16 128 - 3 x(X - 4)=23 [ (4xX+28) x 3+55 ] :5=35
\(\left(5\cdot x+7\right):2=16\) \(128-3\cdot\left(x-4\right)=23\)
\(\left(5\cdot x+7\right)=16\cdot2\) \(3\cdot\left(x-4\right)=128-23\) \([\left(4\cdot x+28\right)\cdot3+55]:5=35\)
\(\left(5\cdot x+7\right)=32\) \(3\cdot\left(x-4\right)=105\) \([\left(4\cdot x+28\right)\cdot3+55]=35\cdot5\)
\(5\cdot x=32-7\) \(x-4=105:3\) \([\left(4\cdot x+28\right)\cdot3+55]=175\)
\(5\cdot x=25\) \(x-4=35\) \(\left(4\cdot x+28\right)\cdot3=175-55\)
\(x=25:5\) \(x=35+4\) \(\left(4\cdot x+28\right)\cdot3=120\)
\(x=5\) \(x=39\) \(\left(4\cdot x+28\right)=120:3\)
\((4\cdot x+28)=40\)
\(4\cdot x=40-28\)
\(4\cdot x=12\)
\(x=12:4\)
\(x=3\)
Chúc bạn hok tốt !
a) 5x X+7=16x2 b)3x(X-4)=128-23 c)(4x X +28 ) x 3 + 55 = 35 x 5
5xX+7=32 3x(X-4)=105 (4x X + 28) x3 +55 =175
5xX=32-7 X-4 = 105 : 3 (4x X + 28 ) x3 = 175 -55
5xX=25 X-4 = 35 (4x X + 28 ) x3 = 120
X=25:5 X = 35 + 4 4x X + 28 = 120 : 3=40
X=5 X = 39 X = (40-28):4=3
Tìm x: a, 213-2x X=47
b, 3x(x+1)-300=906
c,7/3-2/3xX=1/4
d,2/5xX+7/8=2
a) 213 - 2 x X = 47
2 x X = 213 - 47
2 x X = 166
X = 166 : 2
X = 83
b) 3 x ( X + 1 ) - 300 = 906
3 x ( X + 1 ) = 906 + 300
3 x ( X + 1 ) = 1206
X + 1 = 1206 : 3
X + 1 = 402
X = 402 - 1
X = 401
c) \(\frac{7}{3}-\frac{2}{3}\times x=\frac{1}{4}\)
\(\frac{2}{3}\times x=\frac{7}{3}-\frac{1}{4}\)
\(\frac{2}{3}\times x=\frac{25}{12}\)
\(x=\frac{25}{12}:\frac{2}{3}\)
\(x=\frac{25}{8}\)
d) \(\frac{2}{5}\times x+\frac{7}{8}=2\)
\(\frac{2}{5}\times x=2-\frac{7}{8}\)
\(\frac{2}{5}\times x=\frac{9}{8}\)
\(x=\frac{9}{8}:\frac{2}{5}\)
\(x=\frac{45}{16}\)
Học tốt #
a) \(213-2\cdot x=47\)\(\Leftrightarrow2\cdot x=166\Leftrightarrow x=83\)
b)\(3x\left(x+1\right)-300=906\Leftrightarrow3x\left(x+1\right)=606\)
\(\Leftrightarrow x\left(x+1\right)=202\Leftrightarrow x^2+x-202=0\)
\(\Leftrightarrow\left(x+\frac{1}{2}\right)^2-202,25=0\)\(\Leftrightarrow\orbr{\begin{cases}x+\frac{1}{2}=\sqrt{202,25}\\x+\frac{1}{2}=-\sqrt{202,25}\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=\sqrt{202,25}-0,5\\x=-\sqrt{202,25}-0,5\end{cases}}\)
a) 213 - 2*x = 47
2*x = 213 - 47
2*x = 126
x = 63
các phần cn lại bn lm tương tự nha!
b)0,5xx+2/3xx+2/3=7/12
c)3/5-2/15:x=1/2
d)50%xx-2va1/2=2va5/6
e)(2va4/5xx-50):2/3-51
f)(4va1/2-2xx)x3va2/3=11/15
g)02/5-(2va1/2xx-3):15=1/10
h)(3/4+x)x1/1+5va1/6-1va1/6