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29 tháng 7 2018

a)

\(1.24^2-0.24^2\\ =\left(\dfrac{31}{25}\right)^2-\left(\dfrac{6}{25}\right)^2\\ =\left(\dfrac{31}{25}-\dfrac{6}{25}\right)\left(\dfrac{31}{25}+\dfrac{6}{25}\right)=\dfrac{37}{25}\)

b)

\(\dfrac{1}{8}-8x^3\\ =\left(\dfrac{1}{2}\right)^3-\left(2x\right)^3\\ =\left(\dfrac{1}{2}-2x\right)\left(\dfrac{1}{4}+2x+4x^2\right)\)

c)

\(x^2-x+\dfrac{1}{4}\\ =x^2-2.x.\dfrac{1}{2}+\left(\dfrac{1}{2}\right)^2\\ =\left(x-\dfrac{1}{2}\right)^2\)

d)

\(x^2+x+\dfrac{1}{4}\\ =x^2+2.x.\dfrac{1}{2}+\left(\dfrac{1}{2}\right)^2\\ =\left(x+\dfrac{1}{2}\right)^2\)

29 tháng 7 2018

Học tốt nha bạn!!!haha

b: \(=\left(\dfrac{1}{2}-2x\right)\left(\dfrac{1}{4}+x+4x^2\right)\)

c: \(=\left(x-\dfrac{1}{2}\right)^2\)

d: \(=\left(x+\dfrac{1}{2}\right)^2\)

15 tháng 8 2018

a , \(16x^2+8x+1=\left(4x\right)^2+2.4x.1+1^2=\left(4x+1\right)^2\)

b , \(x^2-x+\dfrac{1}{4}=x^2-2.x.\dfrac{1}{2}+\left(\dfrac{1}{2}\right)^2=\left(x-\dfrac{1}{2}\right)^2\)

15 tháng 8 2018

a,(4x+1)2 e,\(\left(\dfrac{3}{2}x-\dfrac{2}{5}\right)^2\)

b,(x-\(\dfrac{1}{2}\))2 g,\(\left(xy+1\right)^2\)

c,(\(x+\dfrac{3}{2}\))2 h,\(\left(x+5\right)^2\)

d,\(\left(x-\dfrac{5}{4}\right)^2\) i,\(-\left(x-6\right)^2\)

k,\(-\left(2x+3\right)^2\)

4 tháng 8 2018

b,\(\dfrac{4}{9}x^2+4x+9=\left(\dfrac{2}{3}x\right)^2+2.\dfrac{2}{3}x.3+3^2=\left(\dfrac{2}{3}x+3\right)^2\)

c, \(x^3+9x^2+27x+27=x^3+3.x^2.3+3.x.3^2+3^3=\left(x+3\right)^3\)

d, \(\dfrac{1}{8}-\dfrac{3}{4}x+\dfrac{3}{2}x^2-x^3=\left(\dfrac{1}{2}\right)^3-3.\left(\dfrac{1}{2}\right)^2.x+3.\dfrac{1}{2}.x^2-x^3=\left(\dfrac{1}{2}-x\right)^3\)

TK MIK vui

27 tháng 6 2017

Bài 1:

a) -16 +(x-3)2

<=> (x-3)2-16

<=> (x-3)2 -42

<=> (x-3-4)(x-3+4)

<=> (x-7)(x+1)

b) 64+16y+y2

<=> y2 + 2.8.y + 82

<=> (y+8)2

c) \(\dfrac{1}{8}-8x^3\)

\(\Leftrightarrow\left(\dfrac{1}{2}\right)^3-\left(2x\right)^3\)

\(\Leftrightarrow\left(\dfrac{1}{2}-2x\right)\left(\dfrac{1}{4}+x+4x^2\right)\)

d)\(x^2-x+\dfrac{1}{4}\)

\(\Leftrightarrow x^2-2.\dfrac{1}{2}.x+\left(\dfrac{1}{2}\right)^2\)

\(\Leftrightarrow\left(x-\dfrac{1}{2}\right)^2\)

e) x4 + 4x2 + 4

<=> (x2)2 + 2.2.x2 +22

<=> (x2 + 2)2

g)\(8x^3+60x^2y+150xy^2+125y^3\)

\(\Leftrightarrow\left(2x+5y\right)^3\)

28 tháng 6 2017

Ban giup minh bai 2 luon voi nha Hậu Trần Công

26 tháng 7 2017

a) x2 +4x+4 = ( x + 2 )2

b) 16x2 - 8xy + y2 = ( 4x - y )2

c)9a2 +16b2 - 24ab = ( 3a - 4y ) 2

d) x2 - x + \(\dfrac{1}{4}\)= ( x - \(\dfrac{1}{2}\))2

e) y2 + \(\dfrac{1}{2}y\) + \(\dfrac{1}{16}\) = ( y + \(\dfrac{1}{4}\))2

26 tháng 7 2018

Những hằng đẳng thức đáng nhớ

4 tháng 7 2017

B3;a,ĐKXĐ:\(x\ne\pm4\)

A=\(\left(\dfrac{4}{x-4}-\dfrac{4}{x+4}\right)\dfrac{x^2+8x+16}{32}=\left(\dfrac{4x+16}{x^2-16}-\dfrac{4x-16}{x^2-16}\right)\dfrac{x^2+2.4x+4^2}{32}=\left(\dfrac{4x+16-4x+16}{x^2-16}\right)\dfrac{\left(x+4\right)^2}{32}=\left(\dfrac{32}{x^2-16}\right)\dfrac{\left(x+4\right)^2}{32}=\dfrac{32\left(x+4\right)^2}{32.\left(x-4\right)\left(x+4\right)}=\dfrac{x+4}{x-4}\\ \\ \\ \\ \\ \\ b,Tacó\dfrac{x+4}{x-4}=\dfrac{1}{3}\Leftrightarrow3x+12=x-4\Leftrightarrow x=-8\left(TM\right)c,TAcó\dfrac{x+4}{x-4}=3\Leftrightarrow x+4=3x-12\Leftrightarrow x=8\left(TM\right)\)