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a. \(x^2+4x+4=x^2+2\cdot x\cdot2+2^2=\left(x+2\right)^2\)
b. \(4x^2-4x+1=\left(2x\right)^2-2\cdot2x\cdot1+1^2=\left(2x-1\right)^2\)
c. \(4x^2+12x+9=\left(2x\right)^2+2\cdot2x\cdot3+3^2=\left(2x+3\right)^2\)
d. \(9x^2+30x+25=\left(3x\right)^2+2\cdot3x\cdot5+5^2=\left(3x+5\right)^2\)
e. \(4x^2-20x+25=\left(2x\right)^2-2\cdot2x\cdot5+5^2=\left(2x+5\right)^2\)
a) \(x^2+4x+4=x^2+2.2x+2^2=\left(x+2\right)^2\)
\(\left(x^2+4x+4\right)\div\left(x+2\right)=x+2\)
b) \(x^3-1=\left(x-1\right)\left(x^2+x+1\right)\)
\(\left(x^3-1\right)\div\left(x-1\right)=x^2+x+1\)
c) \(x^3+6x^2+12x+8=x^3+3.x^2.2+3.x.2^2+2^3=\left(x+2\right)^3\)
\(\left(x^3+6x^2+12x+8\right)\div\left(x+2\right)=\left(x+2\right)^2\)
Ta có:
\(\dfrac{x}{x-4}=\dfrac{...}{x^2-16}=\dfrac{...}{\left(x-4\right)\left(x+4\right)}\)
\(\Rightarrow\dfrac{...}{\left(x-4\right)\left(x+4\right)}=\dfrac{x}{x-4}=\dfrac{x\left(x+4\right)}{\left(x-4\right)\left(x+4\right)}=\dfrac{x^2+4x}{\left(x-4\right)\left(x+4\right)}\)
Vậy đa thức cần điền vào dấu ... là \(x^2+4x\)
b)(y-2)^3=y^3-8+12y-6y^2
c)8x^3+y^3=(2x+y)(4x^2+y^2-4xy)
2)
=(xy+2/3)^2
Bài 3:
a) \(\left(4x^2+4xy+y^2\right):\left(2x+y\right)=\left(2x+y\right)^2:\left(2x+y\right)=2x+y\)
b) \(\left(27x^3+1\right):\left(3x+1\right)=\left(3x+1\right)\left(9x^2-9x+1\right):\left(3x+1\right)=9x^2-9x+1\)
c) \(\left(x^2-6xy+9y^2\right):\left(3y-x\right)=\left(x-3y\right)^2:\left(3y-x\right)=\left(3y-x\right)^2:\left(3y-x\right)=3y-x\)
d) \(\left(8x^3-1\right):\left(4x^2+2x+1\right)=\left(2x-1\right)\left(4x^2+2x+1\right):\left(4x^2+2x+1\right)=2x-1\)
Bài 4: Tương tự bài 3 '-'
Bài 4 :
a ) ( 4x4 - 9 ) : ( 2x2 - 3 )
= ( 2x2 + 3 )( 2x2 - 3 ) : ( 2x2 - 3 )
= 2x2 + 3
b ) ( 8x3 - 27 ) : ( 4x2 + 6x + 9 )
= ( 2x - 3 )( 4x2 + 6x + 9 ) : ( 4x2 + 6x + 9 )
= 2x - 3
\(x^4+4x^2+\circledast=\left(\circledast+\circledast\right)^2\\ \left(x^2\right)^2+2\cdot2\cdot x^2+4=\left(x^2+2\right)^2\)
các vị trí * lần lượt là: \(4;x^2;2\)