20 10 adult college entrance examination mathematics fill-in-the-blank questions

1. Distance from point P(x0, y0) to a straight line: AX+BY+C=0 is d=|A*X0+B*Y0+C|/ root sign (A 2+B 2).

The center of the circle is (0,0), so d= 1/ (2 under the root sign) = (2 under the root sign)/2.

2.y' = 6x2, tangent slope k=6* 1=6.

The tangent equation is Y=6(X- 1)+3, which is simplified to 6X-Y-3=0.

3. Let the expression of this function be ax 2+bx+c = 0 (1), because it spans points (0,0) and (-4,0).

So C=0,

16A-4B=0，B=4A，

So the formula (1) can be simplified as ax 2+4ax = 0, and further simplified as x 2+4x = (x+2) 2-4 = 0.

So the equation of symmetry axis is X = -2.

Hope to adopt ~