实数x,y满足x²-2x-4y=6,记t=x-2y,则t的取值范围是

实数x,y满足x²-2x-4y=6,记t=x-2y,则t的取值范围是
实数x,y满足x²-2x-4y=6,记t=x-2y,则t的取值范围是

实数x,y满足x²-2x-4y=6,记t=x-2y,则t的取值范围是
x²-2x-4y=6
=>
x^2 - 4x + 2x - 4y = 6
=>
2x-4y = -(x^2 -4x -6)
x-2y = -1/2 (x-2)^2 + 10