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a) \(x^3+3x^2+3x+1=\left(x+1\right)^3\)
b) \(27y^3-9y^2+y-\frac{1}{27}=\left(3y-\frac{1}{3}\right)^3\)
c) \(8x^6+12x^4y+6x^2y+y^3=\left(2x^2+y\right)^3\)
d) \(\left(x+y\right)^3\left(x-y\right)^3=\left(x^2-y^2\right)^3\)
e) \(\left(x^2-y^2\right)^2\left(x+y\right)\left(x-y\right)=\left(x^2-y^2\right)^3\)
a) Ta có: \(x^3+12x^2+48x+64\)
\(=x^3+3\cdot x^2\cdot4+3\cdot x\cdot4^2+4^3\)
\(=\left(x+4\right)^3\)
b) Ta có: \(x^3-12x^2+48x-64\)
\(=x^3-3\cdot x^2\cdot4+3\cdot x\cdot4^2-4^3\)
\(=\left(x-4\right)^3\)
c) Ta có: \(8x^3+12x^2y+6xy^2+y^3\)
\(=\left(2x\right)^3+3\cdot\left(2x\right)^2\cdot y+3\cdot2x\cdot y^2+y^3\)
\(=\left(2x+y\right)^3\)
d)Sửa đề: \(x^3-3x^2+3x-1\)
Ta có: \(x^3-3x^2+3x-1\)
\(=x^3-3\cdot x^2\cdot1+3\cdot x\cdot1^2-1^3\)
\(=\left(x-1\right)^3\)
e) Ta có: \(8-12x+6x^2-x^3\)
\(=2^3-3\cdot2^2\cdot x+3\cdot2\cdot x^2-x^3\)
\(=\left(2-x\right)^3\)
f) Ta có: \(-27y^3+9y^2-y+\frac{1}{27}\)
\(=\left(\frac{1}{3}\right)^3+3\cdot\left(\frac{1}{3}\right)^2\cdot\left(-3y\right)+3\cdot\frac{1}{3}\cdot\left(-3y\right)^{^2}+\left(-3y\right)^3\)
\(=\left(\frac{1}{3}-3y\right)^3\)
Bài 1 : Viết các đa thức sau dưới dạng lập phương của một tổng hoặc lập phương của một hiệu
a,8x3+12x2y+6xy2+y3
= (2x)3 + 3.(2x)2.y + 3.2x.y2 + y3
= ( 2x + y )3
b,x3+3x2+3x+1
= x3 + 3.x2.1 + 3.x.12 + 13
=(x + 1)3
c,x3−3x2+2x−1
= x3 - 3.x2.1+ 3.x.12 - 13
= (x - 1)3
d,6
= 33 + 3.32.y2 + 3.3.y4 + (y2)3
= ( 3 + y2 ) 3
cho hỏi lập phương của 1 tổng hay 1 hiệu hay tổng hiệu 2 lập phương vậy
bn viết đề vậy mk cx bí thui haizzzzzz
a)
A = \(\left(2x\right)^3+3.\left(2x\right)^2.y+3.\left(2x\right).y+y^3\)
= \(\left(2x+y\right)^3\)
b)
\(B=x^3-3.x^2.1+3.x.1-1^3\)
= \(\left(x-1\right)^3\)
a) \(8-12x+6x^2-x^3\)
\(=-x^3+8+6x^2-12x\)
\(=-\left(x^3-2^3\right)+6x\left(x-2\right)\)
\(=-\left(x-2\right)\left(x^2+2x+4\right)+6x\left(x-2\right)\)
\(=\left(x-2\right)\left(-x^2-2x-4+6x\right)\)
\(=\left(x-2\right)\left(-x^2+4x-4\right)\)
\(=-\left(x-2\right)\left(x-2\right)^2\)
\(=-\left(x-2\right)^3\)
b) \(48x+64+x^3+12x^2\)
\(=x^3+3.4.x^2+3.x.4^2+4^3\)
\(=\left(x+4\right)^3\)
c) \(-9y^2+y-\dfrac{1}{27}+27y^3\)
\(=27y^3-9y^2+y-\dfrac{1}{27}\)
\(=\left(3y\right)^3-3.\left(3y\right)^2.\dfrac{1}{3}+3.3y.\left(\dfrac{1}{3}\right)^2-\left(\dfrac{1}{3}\right)^3\)
\(=\left(3y-\dfrac{1}{3}\right)^3\)
d) \(8x^3+150x-125-60x^2\)
\(=8x^3-60x^2+150x-125\)
\(=\left(2x\right)^3-3.\left(2x\right)^2.5+3.2x.5^2-5^3\)
\(=\left(2x-5\right)^3\)
a, \(8-12x+6x^2-x^3=-\left(x^3-6x^2+12x-8\right)\)
\(=-\left(x^3-2x^2-4x^2+8x+4x-8\right)\)
\(=-\left(x-2\right)^3\)
b, \(48x+64+x^3+12x^2=x^3+4x^2+8x^2+32x+16x+24\)
\(=\left(x+4\right)^3\)
c, \(-9y^2+y-\dfrac{1}{7}+27y^3\)
(sai đề)
d, \(8x^3+150x-125-60x^2=8x^3-20x^2-40x^2+100x+50x-125\)
\(=4x^2\left(2x-5\right)-20x\left(2x-5\right)+25\left(2x-5\right)\)
\(=\left(2x-5\right)\left(4x^2-20x+25\right)=\left(2x-5\right)\left(2x-5\right)^2\)
\(=\left(2x-5\right)^3\)
Chúc bạn học tốt!!!
1, \(x^2+2xy+y^2=\left(x+y\right)^2\)
2, \(4x^2+12x+9=\left(2x\right)^2+2\cdot3\cdot2x+3^2=\left(2x+3\right)^2\)
3, \(x^2+5x+\dfrac{25}{4}=x^2+2\cdot\dfrac{5}{2}\cdot x+\left(\dfrac{5}{2}\right)^2=\left(x+\dfrac{5}{2}\right)^2\)
4, \(16x^2-8x+1=\left(4x\right)^2-2\cdot4x\cdot1+1^2=\left(4x-1\right)^2\)
5, \(x^2+x+\dfrac{1}{4}=x^2+2\cdot\dfrac{1}{2}\cdot x+\left(\dfrac{1}{2}\right)^2=\left(x+\dfrac{1}{2}\right)^2\)
1: =(x+y)^2
2: =(2x+3)^2
3: =(x+5/2)^2
4: =(4x-1)^2
5: =(x+1/2)^2
6: =(x-3/2)^2
7: =(x+1)^3
8: =(1/2x+1)^2
9: =(3y-1/3)^3
10: =(2x+y)^3
2:
-8x^6-12x^4y-6x^2y^2-y^3
=-(8x^6+12x^4y+6x^2y^2+y^3)
=-(2x^2+y)^3
3:
=(1/3)^2-(2x-y)^2
=(1/3-2x+y)(1/3+2x-y)
a, \(25x^2+5xy+\frac{1}{4}y^2=\left(5x\right)^2+2.5x.\frac{1}{2}y+\left(\frac{1}{2}y\right)^2\)
\(=\left(5x+\frac{1}{2}y\right)^2\)
b, \(9x^2+12x+4=\left(3x\right)^2+2.3x.2+2^2=\left(3x+2\right)^2\)
c, \(x^2-6x+5-y^2-4y=\left(x^2-6x+9\right)-\left(y^2+4y+4\right)\)
\(=\left(x-3\right)^2-\left(y+2\right)^2=\left(x-y-5\right)\left(x+y-1\right)\)
d, \(\left(2x-y\right)^2+4\left(x+y\right)^2-4\left(2x-y\right)\left(x+y\right)\)
\(=\left(2x-y\right)^2-2\left(2x-y\right)\left(2x+2y\right)+\left(2x+2y\right)^2\)
\(=\left(2x-y+2x+2y\right)^2=\left(4x+y\right)^2\)
a; \(x^3\) + 3\(x^2\) + 3\(x\) + 1
= \(x^3\) + 3\(x^2\).1 + 3\(x\).12 + 13
= (\(x\) + 1)3
b; 27y3 - 9y2 + y - \(\dfrac{1}{27}\)
= (3y)3 - 3(3y)2.\(\dfrac{1}{3}\) + 3.(3y).(\(\dfrac{1}{3}\))2 - (\(\dfrac{1}{3}\))3
= (3y - \(\dfrac{1}{3}\))3