a) \(x^2-9=\left(x-3\right)\left(x+3\right)\)

b) \(x^2+1-\dfrac{41}{25}=x^2-\dfrac{16}{25}=\left(x-\dfrac{4}{5}\right)\left(x+\dfrac{4}{5}\right)\)

a) x=60

b) x=107

f) x=2

.....

CHO MÌNH BIẾT CẢ CÁCH LÀM NHA

a) 315 + ( 146 - x ) = 401

<=> 146 - x = 401 - 315

<=> 146 - x = 86

<=> x = 60

Vậy x  = 60

chết r đăng nhầm

Bài 1:

a) \(x^2-x+1\)

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

\(=\left(x-\dfrac{1}{2}\right)^2+\dfrac{3}{4}\ge\dfrac{3}{4}>0;\forall x\)

b) \(25x^2+10x+2\)

\(=25x^2+10x+1+1\)

\(=\left(5x+1\right)^2+1\ge1>0;\forall x\)

c) \(3x^2+2x+14\)

\(=3x^2+2x+\dfrac{1}{3}+\dfrac{41}{3}\)

\(=\left(\sqrt{3}x+\dfrac{\sqrt{3}}{3}\right)^2+\dfrac{41}{3}\ge\dfrac{41}{3}>0;\forall x\)

d) \(2x^2+y^2-2xy-2x+2\)

\(=x^2+y^2-2xy-2x+x^2+1+1\)

\(=\left(x-y\right)^2+\left(x-1\right)^2+1\ge1>0;\forall x\)

Vậy ...

Bài 4:

a: \(=7xy\left(2-3-4\right)=-35xy\)

b: \(=\left(x-5\right)\left(x+y\right)\)

c: \(=10x\left(x-y\right)+8\left(x-y\right)=2\left(x-y\right)\left(5x+4\right)\)

d: \(=\left(x+y\right)^3-\left(x+y\right)\)

=(x+y)(x+y+1)(x+y-1)

e: =x^2+8x-x-8

=(x+8)(x-1)

f: \(=2x^2-4x+x-2=\left(x-2\right)\left(2x+1\right)\)

g: =-5x^2+15x+x-3

=(x-3)(-5x+1)

h: =x^2-3xy+xy-3y^2

=x(x-3y)+y(x-3y)

=(x-3y)*(x+y)

Bài 4:

a: \(=7xy\left(2-3-4\right)=-35xy\)

b: \(=\left(x-5\right)\left(x+y\right)\)

c: \(=10x\left(x-y\right)+8\left(x-y\right)=2\left(x-y\right)\left(5x+4\right)\)

d: \(=\left(x+y\right)^3-\left(x+y\right)\)

=(x+y)(x+y+1)(x+y-1)

e: =x^2+8x-x-8

=(x+8)(x-1)

f: \(=2x^2-4x+x-2=\left(x-2\right)\left(2x+1\right)\)

g: =-5x^2+15x+x-3

=(x-3)(-5x+1)

h: =x^2-3xy+xy-3y^2

=x(x-3y)+y(x-3y)

=(x-3y)*(x+y)

Lời giải:

Ta có:

\(A=\left(2x-1\right)^2-\left(4x^2-1\right)=0\)

<=> \(\left(2x\right)^2-2.2x+1-\left(4x^2-1\right)=0\)

<=> \(4x^2-4x+1-4x^2+1=0\)

<=>\(-4x+2=0\)

<=> \(-4x=-2\)

<=> \(x=\frac{1}{2}\)

Vậy: \(x=\frac{1}{2}\)

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