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\(a,3x-3y=3\left(x-y\right)\\ b,4x^2y-2xy^2+6xy=2xy\left(2x-y+3\right)\\ c,10ab-5a^2=5a\left(2b-a\right)\\ d,3\left(x+y\right)+y\left(x+y\right)=\left(x+y\right)\left(3+y\right)\\ e,x^2-y^2+3x+3y=\left(x-y\right)\left(x+y\right)+3\left(x+y\right)=\left(x+y\right)\left(x-y+3\right)\\ f,ab-a-2b+2=a\left(b-1\right)-2\left(b-1\right)=\left(a-2\right)\left(b-1\right)\)
\(g,x^2+2xy+y^2-16=\left(x+y\right)^2-4^2=\left(x+y+4\right)\left(x+y-4\right)\\ h,a^2-b^2+2a+1=\left(a^2+2a+1\right)-b^2=\left(a+1\right)^2-b^2=\left(a+b+1\right)\left(a-b+1\right)\\ i,x^3+4x^2+4=x\left(x^2+4x+4\right)=x\left(x+2\right)^2\)
\(\left(x^2+1\right)\left(x-2\right)+2x=4\Leftrightarrow x^3-2x^2+x-2+2x-4=0\Leftrightarrow x^3-2x^2+3x-6=0\Leftrightarrow\left(x-2\right)\left(x^2+3\right)=0\Leftrightarrow x-2=0\Leftrightarrow x=2\)(do \(x^2+3\ge3>0\))
Ta có (x+1)^3 - (x-1)^3
=(x3+3x2+3x+1)-(x3-3x2+3x-1)
= x3 + 3x2 +3x +1 - x3 + 3x2 -3x + 1
=6x2 + 2
Vậy biểu thức này có phụ thuộc vào biến x (vì vẫn còn 6x2)
Chúc bạn học tốt!
Lời giải:
1.
$x^3+3x^2-16x-48=(x^3+3x^2)-(16x+48)=x^2(x+3)-16(x+3)$
$=(x+3)(x^2-16)=(x+3)(x-4)(x+4)$
2.
$4x(x-3y)+12y(3y-x)=4x(x-3y)-12y(x-3y)=(x-3y)(4x-12y)=4(x-3y)(x-3y)=4(x-3y)^2$
3.
$x^3+2x^2-2x-1=(x^3-x^2)+(3x^2-3x)+(x-1)=x^2(x-1)+3x(x-1)+(x-1)$
$=(x-1)(x^2+3x+1)$
Bài 3:
\(a,=3x\left(y-4x+6y^2\right)\\ b,=5xy\left(x^2-6x+9\right)=5xy\left(x-3\right)^2\\ d,=\left(x+y\right)\left(x-12\right)\\ f,=2x\left(x-y\right)\left(5x-4y\right)\\ g,=\left(x-2\right)\left(x-2+3x\right)=\left(x-2\right)\left(4x-2\right)=2\left(x-2\right)\left(2x-1\right)\\ h,=x^2\left(1-5x\right)+3xy\left(5x-1\right)=x\left(1-5x\right)\left(x-3y\right)\\ i,=x\left(x-2\right)+4\left(x-2\right)=\left(x+4\right)\left(x-2\right)\\ j,=x^2-2x-3x+6=\left(x-2\right)\left(x-3\right)\\ k,=4x^2-12x+3x-9=\left(x-3\right)\left(4x+3\right)\\ l,=\left(x+5\right)^2-y^2=\left(x-y+5\right)\left(x+y+5\right)\\ m,=x^2-\left(2y-6\right)^2=\left(x-2y+6\right)\left(x+2y-6\right)\\ n,=\left(x^2+5x+4\right)\left(x^2+5x+6\right)-24\\ =\left(x^2+5x+5\right)^2-1-24\\ =\left(x^2+5x+5\right)^2-25\\ =\left(x^2+5x\right)\left(x^2+5x+10\right)\\ =x\left(x+5\right)\left(x^2+5x+10\right)\)
d) \(x^2-y^2-2x+2y\)
\(=\left(x^2-2x+1\right)-\left(y^2-2y+1\right)\)
\(=\left(x-1\right)^2-\left(y-1\right)^2\)
\(=\left(x-1-y+1\right)\left(x-1+y-1\right)\)
\(=\left(x-y\right)\left(x+y-2\right)\)
\(4xy^2-12x^2y+8xy\)
\(=4xy\left(y-3x+2\right)\)
\(3x^2-6xy+3y^2-12z^2\)
\(=3.\left(x^2-2xy+y^2-4z^2\right)\)
\(=3.\left[\left(x-y\right)^2-\left(2z\right)^2\right]\)
\(=3.\left(x-y-2z\right)\left(x-y+2z\right)\)
\(x^4y^4+4=\left[\left(x^2y^2\right)^2+2..x^2y^2.2+2^2\right]-\left(2xy\right)^2\)
\(=\left(x^2y^2+2\right)^2-\left(2xy\right)^2\)
\(=\left(x^2y^2+2-2xy\right)\left(x^2y^2+2+2xy\right)\)
Bài 2:
a: Ta có: \(5x\left(x-1\right)+10x-10=0\)
\(\Leftrightarrow\left(x-1\right)\left(5x+10\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-2\end{matrix}\right.\)
b: Ta có: \(\left(x+2\right)\left(x+3\right)-2x=6\)
\(\Leftrightarrow\left(x+2\right)\left(x+3\right)-2\left(x+3\right)=0\)
\(\Leftrightarrow x\left(x+3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-3\end{matrix}\right.\)
c: Ta có: \(\left(x-1\right)\left(x-2\right)-2=0\)
\(\Leftrightarrow x\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)
\(1,\widehat{D}=360-\widehat{A}-\widehat{B}-\widehat{C}=360-120-50-90=100\)
\(2,\widehat{D}+\widehat{C}=360-\widehat{A}-\widehat{B}=360-50-110=200\\ \Rightarrow4\widehat{D}=200\Rightarrow\widehat{D}=50\Rightarrow\widehat{C}=50\cdot3=150\)
\(a,=3x^2-6x\\ b,=4x^2+x^3-x^3+x^2=5x^2\\ c,=x^2-4x+3x-12=x^2-x-12\\ d,=2x^2+2x-5x-5-2x^2+x=-2x-5\\ e,=x^2+12x+36-x^2=12x+36\\ f,=4a^2-8a+4-4=4a^2+8a\\ g,=9b^2-1+1=9b^2\\ h,=x^3+6x^2+12x+8\\ i,=y^3-9y^2+27y-27\)