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`a)x^2-2x+2+4y^2+4y`
`=x^2-2x+1+4y^2+4y+1`
`=(x-1)^2+(2y+1)^2`
`b)4x^2+y^2+12x+4y+13`
`=4x^2+12x+9+y^2+4y+4`
`=(2x+3)^2+(y+2)^2`
`c)x^2+17+4y^2+8x+4y`
`=x^2+8x+16+4y^2+4y+1`
`=(x+4)^2+(2y+1)^2`
`d)4x^2-12xy+y^2-4y+13`
`=4x^2-12x+9+y^2-4y+4`
`=(2x-3)^2+(y-2)^2`
a) \(x^2-2x+2+4y^2+4y=\left(x-1\right)^2+\left(2y+1\right)^2\)
b) \(4x^2+y^2+12x+4y+13=\left(2x+3\right)^2+\left(y+2\right)^2\)
c) \(x^2+17+4y^2+8x+4y=\left(x+4\right)^2+\left(2y+1\right)^2\)
d) \(4x^2-12x+y^2-4y+13=\left(2x-3\right)^2+\left(y-2\right)^2\)
Lời giải:
a. $x^2+y^2+4y+13-6x$
$=(x^2-6x+9)+(y^2+4y+4)$
$=(x-3)^2+(y+2)^2$
b.
$4x^2-4xy+1+2y^2-2y$
$=(4x^2-4xy+y^2)+(y^2-2y+1)$
$=(2x-y)^2+(y-1)^2$
c.
$x^2-2xy+2y^2+2y+1$
$=(x^2-2xy+y^2)+(y^2+2y+1)$
$=(x-y)^2+(y+1)^2$
a. \(x^2+y^2+4y+12-6x=\left(x^2-6x+9\right)+\left(y^2+4y+4\right)=\left(x-3\right)^2+\left(y+2\right)^2\)b. \(4x^2-4xy+1+2y^2-2y=\left(4x^2-4xy+y^2\right)+\left(y^2-2y+1\right)=\left(2x-y\right)^2+\left(y-1\right)^2\)c. \(x^2-2xy+2y^2+2y+1=\left(x^2-2xy+y^2\right)+\left(y^2+2y+1\right)=\left(x-y\right)^2+\left(y+1\right)^2\)
Ta có
y 2 + 6 y 2 4 - 3 y + 36 = y 2 + 6 y 2 2 - y 2 . 6 + 6 2 = y 2 3 - 6 3
Đáp án cần chọn là: B
4x²y⁴ - 4xy³ + y²
= (2xy²)² - 2.2xy².y + y²
= (2xy² - y)²
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Sửa đề:
(x - 2y)² - 4(x - 2y) + 4
= (x - 2y)² - 2.(x - 2y).2 + 2²
= (x - 2y - 2)²
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25x² - 5xy + 1/4 y²
= (5x)² - 2.5xy.y/2 + (y/2)²
= (5x - y/2)²
\(4x^2y^4-4xy^3+y^2\)
\(=\left(2xy^2\right)^2-2\cdot2xy^2\cdot y+y^2\)
\(=\left(2xy^2-y\right)^2\)
_____
\(\left(x-2y\right)^2-4\left(x-2y\right)+4\)
\(=\left(x-2y\right)^2-2\cdot\left(x-2y\right)\cdot2+2^2\)
\(=\left[\left(x-2y\right)-2\right]^2\)
\(=\left(x-2y-2\right)^2\)
____
\(25x^2-5xy+\dfrac{1}{4}y^2\)
\(=\left(5x\right)^2-2\cdot\dfrac{5}{2}xy+\left(\dfrac{1}{2}y\right)^2\)
\(=\left(5x\right)^2-2\cdot\dfrac{1}{2}y\cdot5x+\left(\dfrac{1}{2}y\right)^2\)
\(=\left(5x-\dfrac{1}{2}y\right)^2\)
\(4x^2-6xy+\dfrac{9}{4}y^2=\left(2x\right)^2-2.2x.\dfrac{3}{2}y+\left(\dfrac{3}{2}y\right)^2=\left(2x-\dfrac{3}{2}y\right)^2\)
2x y 2 + x 2 y 4 + 1 = x y 2 2 + 2.x y 2 .1 + 1 2 = x y 2 + 1 2
x2 - 2 = \(\left(x-\sqrt{2}\right)\left(x+\sqrt{2}\right)\)
\(y^2-13=\left(y-\sqrt{13}\right)\left(y+\sqrt{13}\right)\)