Question

Bài 5 : Tìm x :

a) (x+1)2= (x-3).(x+3)

b) (x+2)2 = (x-5).(x+5)

c) (x+3)2 = (x-7).(x+7)

d) (x+4)2 = (x-6).(x+6)

 

Bài 7 : Tìm x :

a) (x+1)2= (x-3).(x+3)

b) (x+2)2 = (x-5).(x+5)

c) (x+3)2 = (x-7).(x+7)

d) (x+4)2 = (x-6).(x+6)

 

Bài 13 : Tìm x :

a) (x+1)3= x3+ 3x2+ 3x -2

b) (x+2)3= x3+ 6x2+ x

c) (x+3)3= x3+ 9x2+ 4x+1

d) (x+4)3 =x3+ 12x2+ 4x-3

 

Bài 14 : Tìm x :

a) (x-1)3 = x3-3x2 + 2x +1

b) (x-2)3 = x3-6x2 + 2x -3

c) (x-3)3= x3-9x2 + x -4

d) (x-4)3 =x3-12x2 + 3x -4

 

Answer 1

Bài 5:

a: \(\Leftrightarrow x^2+2x+1=x^2-9\)

=>2x=-10

hay x=-5

b: \(\Leftrightarrow x^2+4x+4=x^2-25\)

=>4x=-29

hay x=-29/4

c: \(\Leftrightarrow x^2+6x+9=x^2-49\)

=>6x=-58

hay x=-29/3

d: \(\Leftrightarrow x^2+8x+16=x^2-36\)

=>8x=-52

hay x=-13/2

Answer 2

Bài 5

a, \(x^2+2x+1=x^2-9\Leftrightarrow2x=-10\Leftrightarrow x=-5\)

b, \(x^2+4x+4=x^2-25\Leftrightarrow4x=-29\Leftrightarrow x=-\dfrac{29}{4}\)

c, \(x^2+6x+9=x^2-49\Leftrightarrow5x=-58\Leftrightarrow x=-\dfrac{58}{5}\)

d, \(x^2+8x+16=x^2-36\Leftrightarrow8x=-52\Leftrightarrow x=-\dfrac{52}{8}=-\dfrac{13}{2}\)

Answer 3

Bài 7 : 

a) (x+1)^2= (x-3).(x+3)

<=> \(x^2+2x+1=x^2-9\)

<=> \(2x+10=0\)

=> \(x=-\dfrac{10}{2}=-5\)

b) (x+2)^2 = (x-5).(x+5)

<=> \(x^2+4x+4=x^2-25\)

<=> \(4x+29=0\)

=> x = -29/4

c) (x+3)^2 = (x-7).(x+7)

<=> \(x^2+6x+9=x^2-49\)

<=> \(6x+58=0\)

=> x = -58/6 

d) (x+4)^2 = (x-6).(x+6)

<=> \(x^2+8x+16=x^2-36\)

<=> \(8x+52=0\)

=> x = -52 / 8