giải hpt x2+4y2=5
4x2y+8xy2+5x+10y=1
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1) x³ + 2x² + x
= x(x² + 2x + 1)
= x(x + 1)²
2) 5x³ - 10x² + 5x
= 5x(x² - 2x + 1)
= 5x(x - 1)²
3) 8x²y - 8xy + 2x
= 2x(4xy - 4y + 1)
5) 2x² + 5x³ + x²y
= x²(2 + 5x + y)
6) 4x²y - 8xy² + 18x²y²
= 2xy(2x - 4y + 9xy)
a) 20x - 5y
= 5(4x - y)
b) 5x(x - 1)- 3x(x - 1)
= 2x(x - 1)
c) x(x + y) - 6x - 6y
= x(x + y) - (6x + 6y)
= x(x + y) - 6(x + y)
= (x + y)(x - 6)
d) 6x³ - 9x²
= 3x²(2x - 3)
e) 4x²y - 8xy² + 10x²y²
= 2xy(2x - 4y + 5xy)
g) 20x²y - 12x³
= 4x²(5y - 3x)
h) 8x⁴ + 12x²y⁴ - 16x³y⁴
= 4x²(2x² + 3y⁴ - 4xy⁴)
k) 4xy² + 8xyz
= 4xy(y + 2z)
a, \(x^4+2x^2+1-x^2\)
= \(\left(x^2+1\right)^2-x^2\)
= \(\left(x^2+x+1\right)\left(x^2-x+1\right)\)
b, \(x^4+x^2+1\)
= \(x^4+2x^2+1-x^2\)
= .. ( như phần a )
c, \(y^4+64\)
= \(\left(y^2+8\right)\left(y^2-8\right)\)
d, \(4xy+3z-12y-xz\)
\(=4y\left(x-3\right)-z\left(x-3\right)\)
\(=\left(x-3\right)\left(4y-z\right)\)
e, \(x^2-4xy+4y^2-z^2+6z-9\)
\(=\left(x-2y\right)^2-\left(z-3\right)^2\)
g, \(x^2-4xy+5x+4y^2-10y\)
\(=\left(x^2-4xy+4y^2\right)+\left(5x-10y\right)\)
\(=\left(x-2y\right)^2+5\left(x-2y\right)\)
\(=\left(x-2y\right)\left(x-2y+5\right)\)
h, \(x^2-7x+6\)
\(=x^2-6x-x+6\)
\(=x\left(x-6\right)-\left(x-6\right)\)
\(=\left(x-6\right)\left(x-1\right)\)
i, \(x^3+5x^2+6x+2\)
\(=x^3+x^2+4x^2+4x+2x+2\)
\(=x^2\left(x+1\right)+4x\left(x+1\right)+2\left(x+1\right)\)
\(=\left(x+1\right)\left(x^2+4x+2\right)\)
a) 20x-5y=5(4x-y)
b) 5x(x-1)-3x(x-1)=(5x-3x)(x-1)=2x(x-1)
c) x(x+y)-6x-6y=x(x+y)-(6x+6y)=x(x+y)-6(x+y)=(x-6)(x+y)
d) 6x3-9x2=3x2(2x-3)
e) 4x2y - 8xy2 + 10x2y2=2xy(2x-4y+5xy)
g) 20x2y-12x3=4x2(5y-3x)
h) 8x4+ 12x2y4- 16x3y4 = 4x2(2x2+3y4-4xy4)
k) 4xy2 + 8xyz=4xy(y+2z)
l) 3x(x + 1) - 5y( x + 1 )=(x+1)(3x-5y)
m) 4x2-1=(2x-1)(2x+1)
o) 9-(x-y)2=(3-x+y)(3+x-y)
p) x3+27=(x+3)(x2+3x+9)
n) (x-y)2-4=(x-y-2)(x-y+2)
r) x4 + 2x2 + 1=(x4+x2)+(x2+1)=x2(x2+1)+(x2+1)=(x2+1)2
s) 4x2 - 12xy + 9y2 = (2x-3y)2
t) x2 - x - y2 - y =(x2-y2)-(x+y)=(x-y)(x+y)-(x+y)=(x+y)(x-y-1)
v) x3 - x + y3 - y = (x3+y3)-(x+y)=(x+y)(x2-xy+y2)-(x+y)=(x+y)(x2-xy+y2-1)
\(a,0,5x^3+4x^2y+0,5xy^2\\ =0,5x\left(x^2+8xy+y^2\right)\\ b,0,25x^9\left(y-1\right)+0,75y\left(1-y\right)\\ =0,25x^9\left(y-1\right)-0,75y\left(y-1\right)=\left(y-1\right)\left(0,25x^9-0,75y\right)\\ c,0,25x^2-0,5xy+0,25y^2-0,25\\ =\left(0,5x-0,5y\right)^2-0,25\\ =\left(0,5x-0,5y-0,5\right)\left(0,5x-0,5y+0,5\right)\\ =0,25\left(x-y-1\right)\left(x-y+1\right)\)
Các câu sau tương tự
a: Ta có: \(-x^2+2xy-4y^2+2x+10y-8\)
\(=-x^2+2xy-y^2+2x-2y-3y^2+12y-8\)
\(=-\left(x-y\right)^2+2\left(x-y\right)-1-3y^2+12y-12+5\)
\(=-\left(x-y-1\right)^2-3\left(y^2-4y+4\right)+5=-\left(x-y-1\right)^2-3\left(y-2\right)^2+5\le5\forall x,y\)
Dấu '=' xảy ra khi x-y-1=0 và y-2=0
=>y=2 và x=y+1=2+1=3
b: \(-x^2-y^2+xy+x+y\)
\(=-\frac14\left(4x^2+4y^2-4xy-4x-4y\right)\)
\(=-\frac14\left\lbrack4x^2-4xy+y^2-4x+2y+3y^2-6y\right\rbrack\)
\(=-\frac14\left\lbrack\left(2x-y\right)^2-2\left(2x-y\right)+1+3y^2-6y+3-4\right\rbrack\)
\(=-\frac14\cdot\left\lbrack\left(2x-y-1\right)^2+3\left(y-1\right)^2-4\right\rbrack=-\frac14\left(2x-y-1\right)^2-\frac34\left(y-1\right)^2+1\le1\forall x,y\)
Dấu '=' xảy ra khi y-1=0 và 2x-y-1=0
=>y=1 và 2x=y+1=1+1=2
=>y=1 và x=1
1: \(x^2-x-y^2-y\)
\(=\left(x^2-y^2\right)-\left(x+y\right)\)
\(=\left(x+y\right)\left(x-y\right)-\left(x+y\right)\)
\(=\left(x+y\right)\left(x-y-1\right)\)
2: \(x^2-y^2+x-y\)
\(=\left(x^2-y^2\right)+\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y\right)+\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y+1\right)\)
3: \(3x-3y+x^2-y^2\)
\(=\left(3x-3y\right)+\left(x^2-y^2\right)\)
\(=3\left(x-y\right)+\left(x-y\right)\left(x+y\right)\)
\(=\left(x-y\right)\left(x+y+3\right)\)
4: \(5x-5y+x^2-y^2\)
\(=\left(5x-5y\right)+\left(x^2-y^2\right)\)
\(=5\left(x-y\right)+\left(x-y\right)\left(x+y\right)\)
\(=\left(x-y\right)\left(5+x+y\right)\)
5: \(x^2-5x-y^2-5y\)
\(=\left(x^2-y^2\right)-\left(5x+5y\right)\)
\(=\left(x-y\right)\left(x+y\right)-5\left(x+y\right)\)
\(=\left(x+y\right)\left(x-y-5\right)\)
6: \(x^2-y^2+2x-2y\)
\(=\left(x^2-y^2\right)+\left(2x-2y\right)\)
\(=\left(x-y\right)\left(x+y\right)+2\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y+2\right)\)
7: \(x^2-4y^2+x+2y\)
\(=\left(x^2-4y^2\right)+\left(x+2y\right)\)
\(=\left(x+2y\right)\left(x-2y\right)+\left(x+2y\right)\)
\(=\left(x+2y\right)\left(x-2y+1\right)\)
8: \(x^2-y^2-2x-2y\)
\(=\left(x^2-y^2\right)-\left(2x+2y\right)\)
\(=\left(x-y\right)\left(x+y\right)-2\left(x+y\right)\)
\(=\left(x+y\right)\left(x-y-2\right)\)
9: \(x^2-4y^2+2x+4y\)
\(=\left(x^2-4y^2\right)+\left(2x+4y\right)\)
\(=\left(x-2y\right)\left(x+2y\right)+2\left(x+2y\right)\)
\(=\left(x+2y\right)\left(x-2y+2\right)\)
d) \(4x^2y^2-8xy^2+4y^2=4y^2\left(x^2-2x+1\right)=4y^2\left(x-1\right)^2\)
e) \(x^3y+10x^2y+35xy=xy\left(x^2+10x+35\right)\)
f) \(2x^3-4x^2y+2xy^2-8x=2x\left(x^2-2xy+y^2-4\right)=2x\left[\left(x-y\right)^2-4\right]=2x\left(x-y-2\right)\left(x-y+2\right)\)
g) \(3x^2-9xy-6x+18y=3x\left(x-3y\right)-6\left(x-3y\right)=3\left(x-3y\right)\left(x-2\right)\)
h) \(x^2y^2-3xy^2+2xy-6y=xy\left(xy+2\right)-3y\left(xy+2\right)=\left(xy+2\right)\left(xy-3y\right)=y\left(xy+2\right)\left(x-3\right)\)
d: \(4x^2y^2-8xy^2+4y^2\)
\(=4y^2\left(x^2-2x+1\right)\)
\(=4y^2\left(x-1\right)^2\)
e: \(x^3y+10x^2y+35xy\)
\(=xy\left(x^2+10x+35\right)\)
f: \(2x^3-4x^2y+2xy^2-8x\)
\(=2x\left(x^2-2xy+y^2-4\right)\)
\(=2x\left(x-y-2\right)\left(x-y+2\right)\)
4x2y + 8xy2 + 5x + 10y = 1
<=> (4xy + 5)(x + 2y) = 1
<=> (4xy + x2 + 4y2)(x + 2y) = 1
<=> (x + 2y)3 = 1
<=> x + 2y = 1
<=> x = 1 - 2y
Khi đó x2 + 4y2 = 5
<=> (1 - 2y)2 + 4y2 = 5
<=> 8y2 - 4y - 4 = 0
<=> 2y2 - y - 1 = 0
<=> (y - 1)(2y + 1) = 0
<=> \(\left[{}\begin{matrix}y=1\\y=-\dfrac{1}{2}\end{matrix}\right.\)
Khi y = 1 => x = 1 - 2y = -1
Khi y = \(-\dfrac{1}{2}\Rightarrow x=1-2y=2\)
(x;y) = (-1;1) ; (2;-1/2)