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\(x^7+x^5+1\)
\(=x^7+x^6+x^5-x^6-x^5-x^4+x^5+x^4+x^3-x^3-x^2-x\) \(+x^2+x+1\)
\(=\left(x^7+x^6+x^5\right)-\left(x^6+x^5+x^4\right)+\left(x^5+x^4+x^3\right)-\) \(\left(x^3+x^2+x\right)+\left(x^2+x+1\right)\)
\(=x^5\left(x^2+x+1\right)-x^4\left(x^2+x+1\right)+x^3\left(x^2+x+1\right)-x\left(x^2+x+1\right)\) \(+\left(x^2+x+1\right)\)
\(=\)\(\left(x^5-x^4+x^3-x+1\right)\left(x^2+x+1\right)\)
= (x-y)(x+y)-(x+y)
=(x+y)(x-y-1)
học tốt
- 9y3x – 36y2x= 9xy(y2–4) =9xy(y–4)(y+4)
- 64-y^2 – x^2 – 2xy = 64– (x^2 + 2xy + y^2) = 82 – (x+y)2 = (8 – x –y)(8+x+y)
- x^2 + x – 30= x^2 + x – 25 – 5 = (x2 – 25)(x – 5)= (x-5)(x+5)(x-5)= (x-5)^2 (x+5)
a) \(x^2-5x+5y-y^2\)
\(=\left(x-y\right)\left(x+y\right)-5\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y-5\right)\)
b) \(2\left(x^2+1\right)^2-8x^2\)
\(=2\left[\left(x^2+1\right)^2-4x^2\right]\)
\(=2\left(x^2-2x+1\right)\left(x^2+2x+1\right)\)
\(=2\left(x-1\right)^2\left(x+1\right)^2\)
\(X^2-2XY+Y^2+2X-2Y\)
\(\Leftrightarrow\left(X^2-2XY+Y^2\right)+\left(2X-2Y\right)\)
\(\Leftrightarrow\left(X-Y\right)^2+2\left(X-Y\right)\)
\(\Leftrightarrow\left(X-Y\right)\left(X-Y+2\right)\)
Tk mình nhé.
C1
a) -7x(3x-2)=-21x^2+14x
b) 87^2+26.87+13^2=87^2+2.13.87+13^2=(87+13)^2=100^2
C2
a) (x-5)(x+5)
b)3x(x+5)-2(x+5)=(3x-2)(x+5)=0
\(\Rightarrow\left[\begin{array}{nghiempt}3x-2=0\\x+5=0\end{array}\right.\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=\frac{2}{3}\\x=-5\end{array}\right.\)
Vậy S={-5;2/3}
C3:
a)3x^3-2x^2+2=(x+1)(3x^2-5x-5)-3
b) Để A chia hết cho B=> x+1\(\inƯ\left(-3\right)\)
\(\Rightarrow\begin{cases}x+1=3\\x+1=-3\\x+1=1\\x+1=-1\end{cases}\)\(\Rightarrow\begin{cases}x=2\\x=-4\\x=0\\x=-2\end{cases}\)
1) a) \(x^3-2x^2y+xy^2-25x=x\left(x^2-2xy+y^2-25\right)\)
\(=x\left[\left(x-y\right)^2-5^2\right]=x\left(x-y-5\right)\left(x-y+5\right)\)
b)\(x^2-y^2-2x-2y=\left(x^2-2x+1\right)-\left(y^2+2y+1\right)=\left(x-1\right)^2-\left(y+1\right)^2\)
\(=\left(x-1-y-1\right)\left(x-y+y+1\right)=\left(x-y-2\right)\left(x+1\right)\)
a ) x ^ 2 + 2xy + 7x + 7y + y ^2 + 10 = ( x + y ) ^2 + 7 ( x + y ) + 10 = ( x + y ) ( x + y + 17 )
=(x-y)+(x2-y2)
=(x-y)+(x-y).(x-y)
=(x-y).(x-y+1)
x - y + x2 - y2
= (x - y) + (x2 + y2)
= (x - y) + (x + y) (x - y)
= (x - y) (x + y + 1)
#Hoc tot!!!