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\(a,\left(2x-y\right)^2=4x^2-4xy+y^2\)
\(b,\left(5x-7y^2\right).\left(5x+7y^2\right)=\left(25x^2-49y^4\right)\)
\(c,\left(5x-7y\right)^2.\left(5x+7y\right)^2=\left(25x^2-70xy+49x^2\right).\left(25x^2+70xy+49x^2\right)\)
\(d,\left(\frac{1}{3}x+5y\right).\left(5y-\frac{1}{3}x\right)=25y^2-\frac{1}{9}x^2\)
học tốt nha
a) (2x-y)2 = (2x)2 - 2.2x.y + y2 =4x2-4xy+y2
b)(5x-7y2).(5x+7y2) = (5x)2 - (7y2) 2 =25x2 - 49y4
câu c,d mk ko bít làm
a: \(=-\left[\left(\dfrac{1}{3}ab^2+2a^3b\right)^3\right]\)
\(=\dfrac{-1}{27}a^3b^6-3\cdot\dfrac{1}{9}a^2b^4\cdot2a^3b-3\cdot\dfrac{1}{3}ab^2\cdot4a^6b^2-8a^9b^3\)
\(=\dfrac{-1}{27}a^3b^6-\dfrac{2}{3}a^5b^5-4a^7b^4-8a^9b^3\)
b: \(=x^3+3x^2+3x+1-x^3+3x^2-3x+1-6\left(x^2-1\right)\)
\(=6x^2+2-6x^2+6\)
=8
Bài 1: Khai triển các hằng đẳng thức
a) ( x - 3 )( x2 + 3x + 9 )
= x3 - 33
= x3 - 27
b) ( 5x - 1 )( 1 + 5x + 25x2 )
= ( 5x - 1 )(25x2 + 5x + 1 )
= (5x)3 - 1
= 125x3 - 1
c) ( x2 - 1 ) ( x4 + x2 + 1 )
= (x2)3 - 1
= x6 - 1
a) ( x - 3 )( x2 + 3x + 9 )=x3-9
b) ( 5x - 1 ) ( 1 + 5x + 25x2 )=125x3-1
c) ( x2 - 1 ) ( x4 + x2 + 1 )=x6-1
a) \(\left(m-\dfrac{1}{4}\right)^3=\left(m^3-3m^2.\dfrac{1}{4}+3m\left(\dfrac{1}{4}\right)^2-\left(\dfrac{1}{4}\right)^3\right)\\ =\left(m^3-\dfrac{3}{4}m^2+\dfrac{3}{16}m-\dfrac{1}{64}\right)\)
b)\(\left(\dfrac{2}{3}-n\right)^3=\left(\dfrac{2}{3}\right)^3-3\left(\dfrac{2}{3}\right)^2n+3.\dfrac{2}{3}n^2-n^3\\ =\dfrac{8}{27}-\dfrac{4}{3}n+2n^2-n^3\)
c)\(m^3-125=m^3-5^3=\left(m-5\right)\left(m^2+5m+25\right)\)
d)\(m^3+\dfrac{1}{64}=m^3+\left(\dfrac{1}{4}\right)^3=\left(m+\dfrac{1}{4}\right)\left(m^2-\dfrac{1}{4}m+\dfrac{1}{16}\right)\)
1) \(x^6+1\)
\(=x^6+x^4-x^4+x^2-x^2+1\)
\(=\left(x^6-x^4+x^2\right)+\left(x^4-x^2+1\right)\)
\(=x^2\left(x^4-x^2+1\right)+\left(x^4-x^2+1\right)\)
\(=\left(x^2+1\right)\left(x^4-x^2+1\right)\)
2) \(x^6-y^6\)
\(=\left(x^3+y^3\right)\left(x^3-y^3\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2\right)\left(x-y\right)\left(x^2+xy+y^2\right)\)
\(\left(2x^m+7y^n\right)^2=4x^{2m}+28x^my^n+49y^{2n}\)
\(\left[\left(x-3\right)-z\right]^2=\left(x-3\right)^2-2\left(x-3\right)z+z^2=x^2-6x+9-2xz+6z+z^2\)
\(\left(4a^2-3b^2\right)\left(3b^2+4a^2\right)=\left(4a^2\right)^2-\left(3b^2\right)^2=16a^4-9b^4\)
Tham khảo nhé~