\(a,\left(2x-1\right)^2-\left(x-3\right)\left(x+3\right)-1969\\ =4x^2-4x+1-x^2+9-1969\\ =3x^2-4x-1959\)
\(b,\left(2x-3y\right)\left(2x+3y\right)-\left(2x-y\right)^2\\ =4x^2-9y^2-4x^2+4xy-y^2\\ =8y^2+4xy=4y\left(2y+x\right)\)
\(c,\left(x+3y\right)^2+\left(x+y\right)\left(x-y\right)+280\\ =x^2+6xy+9y^2+x^2-y^2+280\\ =2x^2+8y^2+6xy+280\)
a: \(\left(2x-1\right)^2-\left(x-3\right)\cdot\left(x+3\right)-1969\)
\(=4x^2-4x+1-x^2+9-1969\)
\(=3x^2-4x-1959\)
b: \(\left(2x-3y\right)\left(2x+3y\right)-\left(2x-y\right)^2\)
\(=4x^2-9y^2-4x^2+4xy-y^2\)
\(=-10y^2+4xy\)
a)\(\text{( 2 x − 1 )^2− ( x − 3 ) ( x + 3 ) − 1969}\)
\(\text{= 4x^2 − 4x + 1 − x^2 + 9 − 1969}\)
\(\text{=3x^2− 4 x − 1959}\)
b) \(\text{( 2 x − 3 y ) ( 2 x + 3 y ) − ( 2 x − y )^2}\)
=\(\text{= 4 x^2− 9 y^2− 4 x^2 + 4 x y − y^2}\)
\(\text{= -10 y^2+ 4 x y = -2 y ( 5 y -2 x )}\)
c)\(\text{( x + 3 y )^2 + ( x + y ) ( x − y ) + 280}\)
\(\text{= x^2 + 6 x y + 9 y^2 + x^2 − y^2 + 280}\)
\(\text{= 2 x^2 + 8 y^2 + 6 x y + 280}\)