a,81x^2-..\(2.\left(9x\right).5\)..+25

b,y^2-10y+..\(25\)..

c,.\(4y^2\)..+24xy+36x^2

a,81x^2-.\(2x\left(9x\right).5\)...+25

b,y^2-10y+..\(25\)..

c,..\(4y^2\).+24xy+36x^2

\(\text{a},x-3=0:7\\ x=3\\ b,-2\left(x+1\right)=45-31\\ -2\left(x+1\right)=14\\ X+1=7\\ x=6\\ c,x-35=18\\ x=18+35=53\)

\(\text{a},=25x^2-9+5x^2-5x=30x^2-5x-9\\ b,=x^2+8x+16-x^2+1-16=8x+1\\ c,=4x^2-4x+1+x^2+6x+9-5\left(x^2-49\right)=5x^2+2x+10-5x^2+245=2x+255\)

\(\dfrac{130}{-400}>-\dfrac{39}{72}\\\)

\(\dfrac{375}{10000}< \dfrac{555}{666}\)

Do chu vi = 96 cm 

ma 24 x 4 = 96

=> Canh hình vuông = 24 cm

Diện tích hình vuông la:

\(24x24=576\left(cm^2\right)\)

\(=\left(1274-20\right):14=1254:14=\dfrac{627}{7}\)

\(\dfrac{588}{686}-\dfrac{650}{1430}=\dfrac{31}{77}\\ b,\dfrac{2004}{2010}-\dfrac{8}{670}=\dfrac{66}{67}\)

\(\dfrac{1995x1990x997x1993x1997}{1997x1993x995x1995x1994}=\dfrac{1990x997}{995x1994}=1\)