\(C=4x^2-4x\)

\(C=4x\left(x-1\right)\)

\(D=2x^2+6x-5\)

\(D=2x^2-4x+10x-5\)

\(D=\left(2x^2-4x\right)+\left(10x-5\right)\)

\(D=2x\left(x-2\right)+5\left(2x-1\right)\)

C=4²-4X

C=4X(X-1)

D=2X²+6X-5

D=2X²-4X+10X-5

D=(2X²-4X)+(10X-5)

D=2X(X-2)+5(2X-1)

a, A= x^2-x +1=x^2-1/2.x.2+1/4 + 3/4=(x- 1/2)^2+3/4 lớn hơn hoặc = 3/4

b,c tương tự

\(a,=x^2+2.x.\frac{1}{2}+\frac{1}{4}+\frac{3}{4}=\left(x+\frac{1}{2}\right)^2+\frac{3}{4}\)

\(b,=9x^2+2.3x.\frac{1}{2}+\frac{1}{4}+\frac{19}{4}=\left(3x+\frac{1}{2}\right)^2+\frac{19}{4}\)

\(c,=16x^2-2.4x+1+6=\left(4x-1\right)^2+6\)

\(a,5\left(x-y\right)-3x\left(y-x\right)=5\left(x-y\right)+3x\left(x-y\right)=\left(5+3x\right)\left(x-y\right)\\ b,x^2-4xy+4y^2=\left(x-2y\right)^2\\ c,\left(x+1\right)^2+x\left(5-x\right)=0\\ \Rightarrow x^2+2x+1+5x-x^2=0\\ \Rightarrow7x+1=0\\ \Rightarrow7x=-1\\ \Rightarrow x=-\dfrac{1}{7}\)

a: =(x-y)(5+3x)

c: \(\Leftrightarrow x^2-2x+1+5x-x^2=0\)

hay x=-1/3

20x²-20x+9

=16x²-2.4x+1+6

=(4x-1)²+6

 (x-1)^2-2(x-1)(2y-1)+(2y-1) = [ x-1 - (2y-1)]² = ( x-1-2y+1)² = ( x-2y)²

mk chỉnh lại đề

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

\(=\left[\left(x-1\right)-\left(2y-1\right)\right]^2\)

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

p/s: chúc bạn học tốt

Bài 1: 

a) \(a^2-6a+9=\left(a-3\right)^2\)

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

Bài 2:

a)  \(\Leftrightarrow-9x^2+30x-25+9x^2+18x+9=30\)

\(\Leftrightarrow48x=46\Leftrightarrow x=\dfrac{23}{24}\)

b) \(\Leftrightarrow x^2+8x+16-x^2+1=16\)

\(\Leftrightarrow8x=-1\Leftrightarrow x=-\dfrac{1}{8}\)