Question

[mai khánh huyền]

rút gọn áp dụng hằng đẳng thức

1.  (x-3)*(x+3)-(x-3)^2

2.  (6x+1)^2 + (6x-1)^2-2*(6x+1)*(6x-1)

3.   (3x-1)^2 +2*(3x-1)*(2x+1)+(2x+1)^2

nhớ ghi cách giải nha!!!!

Answer 1

[kudo shinichi]

\(\left(x-3\right)\left(x+3\right)-\left(x-3\right)^2\)

\(=x^2-3^2-x^2+6x-3^2\)

\(=-9-9+6x\)

\(=6x-18\)

Answer 2

[Arima Kousei]

1 ) 

\(\left(x-3\right)\left(x+3\right)-\left(x-3\right)^2\)

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

\(=x^2-9-x^2+6x-9\)

\(=6x-18\)

2 ) 

\(\left(6x+1\right)^2+\left(6x-1\right)^2-2\left(6x+1\right)\left(6x-1\right)\)

\(=\left(6x\right)^2+2.6x.1+1+\left(6x\right)^2-2.6x.1+1-2\left[\left(6x\right)^2-1^2\right]\)

\(=36x^2+12x+1+36x^2-12x+1-2\left(36x^2-1\right)\)

\(=72x^2+1+1-72x^2+2\)

\(=4\)