tim x , y thuoc Z biet
a , 3x-xy+6y=4
b,x^2-3xy=2x-6y=7
tim x va y thuoc z
a,3x - xy + 6y = 4
b,x^2 - 3xy + 2x - 6y = 7
3x -xy + 6y- 18 = 4 -18
x(3-y) + 6(y -3) = -14 => x(y-3) -6(y-3) =14
(y-3)(x-6) =14
y-3 | 1 | -1 | 14 | -14 | 2 | -2 | 7 | -7 |
x-6 | 14 | -14 | 1 | -1 | 7 | -7 | 2 | -2 |
y | 4 | 2 | 17 | -11 | 5 | 1 | 10 | -4 |
x | 20 | -8 | 7 | 5 | 13 | -1 | 8 | 4 |
toan 7 tim x,y,z biet (xy/2y+4x)=(yz/4z+6y)=(zx/6x+2z)=(x^2+y^2+z^2)/2^2+4^2+6^2
Tìm bậc của các đa thức sau:
a) \(x^3y^3+6x^2y^2+12xy-8
\)
b) \(x^2y+2xy^2-3x^3y+4xy^5\)
c) \(x^6y^2+3x^6y^3-7x^5y^7+5x^4y\)
d) \(2x^3+x^4y^5+3xy^7-x^4y^5+10-xy^7\)
e) \(0,5x^2y^3+3x^2y^3z^3-a.x^2y^3-x^4-x^2y^3\) với a là hằng số
a, bậc 6
b, bậc 6
c, bậc 12
d, bậc 9
e, bậc 8
1) PTTNT
a) x^2 - 4x^2y + 4xy
b)x^2 + 3x + x - 3y
2) Tim GTLN
-2x^2 + 3x - 5
3) tim x,y thuoc z
3xy + 6x - y = 7
Bài 2:
\(A=-2x^2+3x-5\)
\(=-2\left(x^2+\frac{3x}{2}-\frac{5}{2}\right)\)
\(=-2\left(x^2-\frac{3x}{2}+\frac{9}{16}\right)-\frac{31}{8}\)
\(=-2\left(x-\frac{3}{4}\right)^2-\frac{31}{8}\le-\frac{31}{8}\)
Dấu = khi \(-2\left(x-\frac{3}{4}\right)^2=0\Leftrightarrow x-\frac{3}{4}=0\Leftrightarrow x=\frac{3}{4}\)
Vậy \(Max_A=-\frac{31}{8}\Leftrightarrow x=\frac{3}{4}\)
Bài 1:
a)x2-4x2y+4xy
=x(x-4xy+y)
b)đề sai
Bài 3:
3yx + 6x - y = 7
<=> x(3y+6) - (3y+6) = 27
<=> (3y+6)(x+1) = 27
Ta có bảng sau:
x+1 | 1 | -1 | 3 | -3 | 9 | -9 | 27 | -27 | |
3y+6 | 27 | -27 | 9 | -9 | 3 | -3 | 1 | -1 | |
x | 0 | -2 | 2 | -4 | 8 | -10 | 26 | -28 | |
y | 7 | -11 | 1 | -5 | -1 | -3 | \(-\frac{5}{3}\) | \(-\frac{7}{3}\) |
Vậy...
1) thực hiện các phép tính sau
a) 3x - 5/ 7+ 4x+ 5/7
b) 5xy - 4x/2x^2y^3 + 3xy+ 4y/2x^2y^3
c) x+1/X-5+x-18/x-5+x+2/x-5
2)
a) 2/x+3 + 1/x
b) x+1/2x-2+(-2x)/x^2-1
c) y - 12/6y- 36+ 6/ y^2- 6y
d) 6y/x+3x+3/2x+6
Phân tích đa thức thành nhân tử x^3-3x^2y+3xy^2-y^3-z^z^3
x^2-y^2+8x+6y+7
x³ - 3x²y + 3xy² - y³ - z³
= (x³ - 3x²y + 3xy² - y³) - z³
= (x - y)³ - z³
= (x - y - z)[(x - y)² + (x - y)z + z²]
= (x - y - z)(x² - 2xy + y² + xz - yz + z³)
--------------------
x² - y² + 8x + 6y + 7
= (x² + 8x + 16) - (y² - 6y + 9)
= (x + 4)² - (y - 3)²
= (x + 4 - y + 3)(x + 4 + y - 3)
= (x - y + 7)(x + y + 1)
a: \(=\left(x^3-3x^2y+3xy^2-y^3\right)-z^3\)
\(=\left(x-y\right)^3-z^3\)
\(=\left(x-y-z\right)\left[\left(x-y\right)^2+z\left(x-y\right)+z^2\right]\)
\(=\left(x-y-z\right)\left(x^2-2xy+y^2+xz-yz+z^2\right)\)
b: \(=x^2+8x+16-y^2+6y-9\)
=(x+4)^2-(y-3)^2
=(x+4+y-3)(x+4-y+3)
=(x+y+1)(x-y+7)
TÌM X,Y
x^2-3xy+6y=10
2x^2-5xy+3x-y+7=0
Tìm x, y biết:
a) (x-1)(y+2)=7
b)x(y - 1) + y = 4
c) xy - 2x + y = 4
d)x^2 - 3xy + 2x - 6y = 5
`@` `\text {Ans}`
`\downarrow`
`a)`
`(x-1)(y+2)=7`
`=> (x - 1)(y + 2) \in` Ư`(7) = {7; 1; -1; -7}`
Ta có bảng sau:
`x - 1` | `7` | `1` | `-1` | `-7` |
`y + 2` | `1` | `7` | `-7` | `-1` |
`x` | `8` | `2` | `0` | `-6` |
`y` | `-1` | `5` | `-9` | `-3` |
Vậy, ta có cặp `(x; y)` thỏa mãn `{-1; 8}; {2; 5}; {-9; 0}; {-6; -3}`
`b)`
`x(y - 1) + y = 4`
`=> x(y - 1) + y - 4 = 0`
`=> x(y - 1) + (y - 1) - 3 = 0`
`=> (x + 1)(y - 1) = 3`
`=> (x + 1)(y - 1) \in` Ư`(3) = {-1; -3; 1; 3}`
Ta có bảng sau:
`x + 1` | `1` | `3` | `-1` | `-3` |
`y - 1` | `3` | `1` | `-3` | `-1` |
`x` | `0` | `2` | `-2` | `-4` |
`y` | `4` | `2` | `-2` | `0` |
Vậy, ta có cặp `(x; y)` thỏa mãn `{0; 4}; {2; 2}; {-2; -2}; {-4; 0}`
a,tim x biet |x-2|+|3-2x|=2x+1
b,tim x,y thuoc Z biet xy+2x-y=5
c, tinh A=(1-1/15)(1-1/21)(1-1/28).....(1-1/210)