\(a)\)  \( 49(y-4)^2-9(y+2)^2\)

\(=[7(y-4)]^2-[3(y+2)]^2\)

\(=[7(y-4)-3(y+2)][7(y-4)+3(y+2)]\)

\(=(7y-28-3y-6)(7y-28+3y+6)\)

\(=(4y-34)(10y-22)\)

\(b)\)   \((a^2+b^2-5)^2-2(ab+2)^2\)

\(=\left(a^2+b^2-5\right)^2-\left[\sqrt{2}\left(ab+2\right)\right]^2\)

Xem lại đề...

\(x^4-x^2+2x-1\)

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

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

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

hk

tốt

\(=-2x^2+6xy-3y^2+25\)

\(=-\left(2x^2-6xy+3y^2\right)+25\)

\(=-\left(2x^2+3y^2\right)+25\)

\(=\left(2x^2-3y^2\right)+25\)

\(=\left(2x^2+3y^2\right).\left(2x^2-3y^2\right)+25\)

quên rùi

\(-4x^2+12xy-9y^2+25=\left(-4x^2+6xy+10x\right)+\left(6xy-9y^2-15y\right)-\left(10x-15y-25\right)\)

\(=2x\left(-2x+3y+5\right)+-3y\left(-2x+3y+5\right)+5\left(-2x+3y+5\right)\)

\(=\left(-2x+3y+5\right)\left(2x-3y+5\right)\)

a, \(\left(4x+5\right)^2=\left(4x+5\right)\left(4x+5\right)=\left[\left(4x+5\right)4x\right]+\left[\left(4x+5\right)5\right]=4x^2+20x+25\)

b, \(\left(5x-2\right)^2=\left(5x-2\right)\left(5x-2\right)=\left[\left(5x-2\right)5x-\left(5x-2\right)2\right]=5x^2-10x+25\)

b, \(8^2-12x^2=\left(8^2-12x^2\right)\left(8^2+12x^2\right)\)

đúng ko :) 

@No name: Bị sai rồi nhé, a,b,c sai hết  :>

a) ( 4x + 5 )² 

= ( 4x )² + 2.4x.5 + 5² 

= 16x² + 40x + 25 

b) ( 5x - 2 )² 

= ( 5x )² - 2.5x.2 + 2² 

= 25x² - 20x + 4 

c) 8² - 12x² 

= 64 - 12x² 

= ( V8 - V12x )( V8 + V12x ) 

*V    là căn 

4: \(\left(2x+3\right)^3-1\)

\(=\left(2x+3-1\right)\left(4x^2+12x+9+2x+3+1\right)\)

\(=\left(2x+2\right)\left(4x^2+14x+13\right)\)

\(=2\left(x+1\right)\left(4x^2+14x+13\right)\)

5: \(4x^2+20xy+25y^2=\left(2x+5y\right)^2\)

6: \(x^4-64xy^3\)

\(=x\left(x^3-64y^3\right)\)

\(=x\left(x-4y\right)\left(x^2+4xy+16y^2\right)\)

\(\left(x^2-2xz+z^2\right)-\left(y^2-2yt+t^2\right)=\left(x-z\right)^2-\left(y-t\right)^2=\left(x-z+y-1\right)\left(x-z-y+t\right)\)

Chúc Bạn học tốt

 T I C K nha

Cau nay ko co dap an sao

a) \(x^6-y^6\)

\(=\left(x^3\right)^2-\left(y^3\right)^2\)

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

\(=\left(x-y\right)\left(x^2+xy+y^2\right)\left(x+y\right)\left(x^2-xy+y^2\right)\)

b) \(10ab+0,25a^2+100b^2\)

\(=\left(0,5a\right)^2+2\cdot0,5a\cdot10b+\left(10b\right)^2\)

\(=\left(0,5a+10b\right)^2\)

c) \(9x^2-xy+\frac{1}{36}y^2\)

\(=\left(3x\right)^2-2\cdot3x\cdot\frac{1}{6}y+\left(\frac{1}{6}y\right)^2\)

\(=\left(3x-\frac{1}{6}y\right)^2\)

\(9\left(x-3y\right)^2-25\left(2x+y\right)^2\)

\(=\left[3\left(x-3y\right)\right]^2-\left[5\left(2x+y\right)\right]^2\)

\(=\left(3x-9y\right)^2-\left(10x+5y\right)^2\)

\(=\left[3x-9y+10x+5y\right]\left[3x-9y-\left(10x+5y\right)\right]\)

\(=\left(13x-4y\right)\left(-7x-14y\right)\)

\(=-7\left(x+2y\right)\left(13x-4y\right)\)

9(x - 3y)² - 25(2x + y)²

= 3².(x - 3y)² - 5².(2x + y)²

= (3x - 9y)² - (10x + 5y)²

= (3x - 9y - 10x - 5y)(3x - 9y + 10x + 5y)

= (-7x - 14y)(13x - 4y)

= -7(x + 2y)(13x - 4y)