a) Ta có: \(4x^2-28xy+49y^2\)

\(=\left(2x\right)^2-2\cdot2x\cdot7y+\left(7y\right)^2\)

\(=\left(2x-7y\right)^2\)

b) Ta có: \(x^2+8xy+16y^2\)

\(=x^2+2\cdot x\cdot4y+\left(4y\right)^2\)

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

c) Ta có: \(x^2-12x+36\)

\(=x^2-2\cdot x\cdot6+6^2\)

\(=\left(x-6\right)^2\)

\(\left(2x-7y\right)^2\)

\(\left(6-x\right)^2\)

4x² - 28xy + 49y²

= (2x)² - 2.2x.7y + (7y)²

= (2x - 7y)²

x² + 8x²y + 16x²y² đề có bị thiếu không , nên mình bổ sung nhé

= x² + 2.x.4xy + (4xy)²

= (x + 4xy)²

36 - 12x + x²

= 6² + 2.6.x + x²

= (6 + x)²

 Chúc bạn học tốt

a 8xy²-12x²y+20xy=4xy(2y-3x+5)

a,=\(4xy\left(2y-3x+5\right)\)

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

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

\(4x^4y-4x^2y^3+12x^3y+12x^2y^2\)

\(=4x^2y\left(x^2-y^2+3x+3y\right)\)

\(=4x^2y\left(x-y-3\right)\left(x+y\right)\)

c: \(\left(x+y\right)^3-x^3-y^3\)

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

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

\(=3xy\left(x+y\right)\)

bài 1:= \(2x\left(x-3\right)-6\left(x-3\right)+2y\left(x-3\right)\)

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

bài 2:P=\(x^2-2x+1+y^2+6y+9+2\)

         P=\(\left(x-1\right)^2+\left(y+3\right)^2+2\ge2\)

vậy Pmin=2 khi x=1 và y=-3

\(12x-9-4x^2=-\left(2x-3\right)^2\\ Sửa:x^3-6x^2y+12xy^2-8y^3=\left(x-2y\right)^3\)

\(a,=6x\left(x-2\right)-7\left(x-2\right)=\left(6x-7\right)\left(x-2\right)\)