2630 +475 - x =612 : 2 + 379
4699 x 2 + x = 64925 : 5 -740
7965 x 4 -2571 x2 = x -6453
6453 - X x 7 - X x 2 = 6048
6453 - X x 7 - X x 2 = 6048
6453 - X x (7 + 2) = 6048
6453 - X x 9 = 6048
6453 - X = 6048 : 9
6453 - X = 672
X = 6453 - 672
X = 5781
Bài1: Tìm x biết:
a) 12 : 5 = x : 1,5
b) x/5 = 3/20
c) 4/x = 10/9
d) x/15 = 60/x
Bài 2:Cho x/3=y/5=z/6, tìm x,y,z biết
a) x + y -z=8
b)x-y+z=(-4)
c)x-2y+3z= (-33)
d) x^2 - 4y^2 + 2z^2 = (-475)
\(a,\dfrac{12}{5}=\dfrac{x}{1,5}\Rightarrow x=\dfrac{12\cdot1,5}{5}=3,6\\ b,\dfrac{x}{5}=\dfrac{3}{20}\Rightarrow x=\dfrac{5\cdot3}{20}=\dfrac{3}{4}\\ c,\dfrac{4}{x}=\dfrac{10}{9}\Rightarrow x=\dfrac{4\cdot9}{10}=\dfrac{18}{5}\\ d,\Rightarrow\dfrac{x}{15}=\dfrac{60}{x}\Rightarrow x^2=60\cdot15=900\Rightarrow\left[{}\begin{matrix}x=30\\x=-30\end{matrix}\right.\\ 2,\)
a, Áp dụng t/c dtsbn:
\(\dfrac{x}{3}=\dfrac{y}{5}=\dfrac{z}{6}=\dfrac{x+y-z}{3+5-6}=\dfrac{8}{2}=4\\ \Rightarrow\left\{{}\begin{matrix}x=12\\y=20\\z=24\end{matrix}\right.\)
b, Áp dụng t/c dtsbn:
\(\dfrac{x}{3}=\dfrac{y}{5}=\dfrac{z}{6}=\dfrac{x-y+z}{3-5+6}=\dfrac{-4}{4}=-1\\ \Rightarrow\left\{{}\begin{matrix}x=-3\\y=-5\\z=-6\end{matrix}\right.\)
c, Áp dụng t/c dtsbn:
\(\dfrac{x}{3}=\dfrac{y}{5}=\dfrac{z}{6}=\dfrac{2y}{10}=\dfrac{3z}{18}=\dfrac{x-2y+3z}{3-10+18}=\dfrac{-33}{11}=-3\\ \Rightarrow\left\{{}\begin{matrix}x=-9\\y=-15\\z=-18\end{matrix}\right.\)
d, Đặt \(\dfrac{x}{3}=\dfrac{y}{5}=\dfrac{z}{6}=k\Rightarrow x=3k;y=5k;z=6k\)
\(x^2-4y^2+2z^2=-475\\ \Rightarrow9k^2-100k^2+72z^2=-475\\ \Rightarrow-19k^2=-475\\ \Rightarrow k^2=25\Rightarrow\left[{}\begin{matrix}k=5\\k=-5\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=15;y=25;z=30\\x=-15;y=-25;z=-30\end{matrix}\right.\)
Tìm x:
a) 3/5 * X = 3/10 , b) X * 2/7 * 3/4 = 5/51 , c) X * 306 = 3610 + 612
a) x = 1/2
b) x = 70/153
c) x = dư ( có sai đề ko bạn )
~Ủng hộ mk nha các bạn~
ừ mình nhầm câu c) là X * 306 = 36108 + 612
1.(x+2)3+(x-3)2-x2(x+5)
2.(2x+3).(x-5)+2x(3-x)+x-10
3.(x+5).(x2-5x+25)-x(x-4)2+16x
4.(-x-2)3+(2x-4).(x2+2x+4)-x2.(x-6)
3: \(\left(x+5\right)\left(x^2-5x+25\right)-x\left(x-4\right)^2+16x\)
\(=x^3+125-x^3+8x^2-16x+16x\)
\(=8x^2+125\)
Bài 5. Tìm x , biết rằng: a) x(x + 5)(x – 5) – (x + 2)(x2 – 2x + 4) = 3
b) (x – 3)3 – (x – 3)(x2 + 3x + 9) + 9(x + 1)2 = 15
c) (x+5)(x2 –5x +25) – (x – 7) = x3
d) (x+2)(x2 – 2x + 4) – x(x2 + 2) = 4
`a) x(x + 5)(x – 5) – (x + 2)(x^2 – 2x + 4) = 3`
`<=>x(x^2-25)-(x^3-8)=3`
`<=>x^3-25x-x^3+8=3`
`<=>-25x=-5`
`<=>x=1/5`
`b) (x – 3)^3 – (x – 3)(x^2 + 3x + 9) + 9(x + 1)^2 = 15`
`<=>x^3-9x^2+27x-27-(x^3-27)+9(x^2+2x+1)=15`
`<=>-9x^2+27x+9x^2+18x+9=15`
`<=>45x+9=15`
`<=>45x=6`
`<=>x=6/45=2/15`
`c) (x+5)(x^2 –5x +25) – (x – 7) = x^3`
`<=>x^3-125-x+7=x^3`
`<=>x^3-x-118=x^3`
`<=>-x-118=0`
`<=>-x=118<=>x=-118`
`d) (x+2)(x^2 – 2x + 4) – x(x^2 + 2) = 4 `
`<=>x^3+8-x^3-2x=4`
`<=>8-2x=4`
`<=>2x=4<=>x=2`
1) ĐKXĐ: \(x\notin\left\{1;-1\right\}\)
Ta có: \(\dfrac{x+1}{x-1}-\dfrac{x-1}{x+1}=\dfrac{4}{x^2-1}\)
\(\Leftrightarrow\dfrac{\left(x+1\right)^2}{\left(x-1\right)\left(x+1\right)}-\dfrac{\left(x-1\right)^2}{\left(x-1\right)\left(x+1\right)}=\dfrac{4}{\left(x-1\right)\left(x+1\right)}\)
Suy ra: \(x^2+2x+1-\left(x^2-2x+1\right)=4\)
\(\Leftrightarrow x^2+2x+1-x^2+2x-1=4\)
\(\Leftrightarrow4x=4\)
hay x=1(loại)
Vậy: \(S=\varnothing\)
2) ĐKXĐ: \(x\notin\left\{2;-2\right\}\)
Ta có: \(\dfrac{x+2}{x-2}+\dfrac{x}{x+2}=2\)
\(\Leftrightarrow\dfrac{\left(x+2\right)^2}{\left(x-2\right)\left(x+2\right)}+\dfrac{x\left(x-2\right)}{\left(x-2\right)\left(x+2\right)}=\dfrac{2\left(x^2-4\right)}{\left(x-2\right)\left(x+2\right)}\)
Suy ra: \(x^2+4x+4+x^2-2x=2x^2-8\)
\(\Leftrightarrow2x^2+2x+4-2x^2-8=0\)
\(\Leftrightarrow2x-4=0\)
\(\Leftrightarrow2x=4\)
hay x=2(loại)
Vậy: \(S=\varnothing\)
Tìm x:
a, x + 4 457 = 4 612
b, x – 827 = 2 484
a, x + 4 457 = 4 612
x = 4612 – 4457
x = 155
b, x – 827 = 2 484
x = 2484 + 827
x = 3311
Giải phương trình chứa ẩn ở mẫu:
a. (x+1)/(x-2) - (x-1)(x+2) = 2(x2 + 2)/(x2 - 4)
b. (2x+1)/(x-1) = 5(x-1)/(x+1)
c. (x-1)/(x+2) - (x)/(x-2) = (5x-2)/(4 - x2)
d. (x-2)/(2+x)-(3)/(x-2)= 2(x-11)/(x2 - 2)
e. (x-1)/(x+1)-(x2 + x - 2)/(x+1)= (x+1)/(x-1) - x - 2
f. (x+1)/(x-1)-(x-1)/(x+1)=(4)/(x2 - 1)
g. (3)/4(x-5) + (15)/(50-2x2)= - (7)/6(x+5)
h. (12)/(8+x3)= 1 + (1)/(x+2)
k. (x+25)/(2x2 - 50)-(x+5)(x2 - 5x)= (5-x)(2x2 + 10x)
\(a,\frac{x+1}{x-2}-\frac{x-1}{x+2}=\frac{2\left(x^2+2\right)}{x^2-4}\)
\(\Leftrightarrow\frac{\left(x+1\right)\left(x+2\right)}{\left(x+2\right)\left(x-2\right)}-\frac{\left(x-1\right)\left(x-2\right)}{\left(x+2\right)\left(x-2\right)}=\frac{2x^2+4}{\left(x-2\right)\left(x+2\right)}\)
\(\Rightarrow x^2+2x+x+2-\left(x^2-2x-x+2\right)=2x^2+4\)
\(\Leftrightarrow x^2+3x+2-x^2+2x+x-2=2x^2+4\)
\(\Leftrightarrow6x=2x^2+4\)
\(\Leftrightarrow2x^2+4-6x=0\)
\(\Leftrightarrow2x^2+4-6x=0\)
\(\Leftrightarrow\left(x-1\right)\left(x+3\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-1=0\\x+3=0\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=1\\x=-3\end{cases}}\)
\(b,\frac{2x+1}{x-1}=\frac{5\left(x-1\right)}{x+1}\)
\(\Leftrightarrow\left(2x+1\right)\left(x+1\right)=5\left(x-1\right)\left(x-1\right)\)
\(\Leftrightarrow2x^2+2x+x+1=5\left(x^2-2x+1\right)\)
\(\Leftrightarrow2x^2+3x+1=5x^2-10x+5\)
\(\Leftrightarrow5x^2-2x^2-10x-3x+5-1=0\)
\(\Leftrightarrow3x^2-13x+4=0\)
\(\Leftrightarrow\left(x-4\right)\left(x-\frac{1}{3}\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-4=0\\x-\frac{1}{3}=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=4\\x=\frac{1}{3}\end{cases}}}\)
\(c,\frac{x-1}{x+2}-\frac{x}{x-2}=\frac{5x-2}{4-x^2}\)
\(\Leftrightarrow\frac{x-1}{x+2}-\frac{x}{x-2}=\frac{2-5x}{x^2-4}\)
\(\Leftrightarrow\frac{\left(x-1\right)\left(x-2\right)}{\left(x+2\right)\left(x-2\right)}-\frac{x\left(x+2\right)}{\left(x-2\right)\left(x+2\right)}=\frac{2-5x}{\left(x-2\right)\left(x+2\right)}\)
\(\Rightarrow x^2-2x-x+2-x^2-2x=2-5x\)
\(\Leftrightarrow-5x+2=2-5x\)
\(\Leftrightarrow-5x+5x=2-2\)
\(\Leftrightarrow0=0\)
=>pt luôn có nghiệm với mọi x.