Almost all the questions you ask are basic questions, reflecting that you are not very clear about the basic concepts of the basic formula. It is suggested to review first, make clear the knowledge points, and then do the questions.

1。 The positional relationship between the straight line 2X+3Y+K=0(K≠2) and 2X+3Y+2=0 is _ _ _ _ _ _ _.

Parallel, the coefficients in front of x and y are the same, but the constant terms are different, so the lines are parallel. (Basic concepts, important)

2。 The curve of equation x2 (the square of x) +Y2-4Y-5=0 is symmetric about _ _ _ _ _ _ _.

Y axis. If x is changed to -x and the original formula remains unchanged, then it is symmetrical about y axis.

3。 The straight line that passes through point (2,3) and is perpendicular to the straight line X-Y+ 1=0 is _ _ _ _ _ _ _ _.

X+y-5 = 0。 A straight line perpendicular to the x-y direction, along the X+Y direction, can be easily obtained by introducing (2,3).

4。 The center coordinate of the circle x2+y2-4y+4 = 0 _ _ _ _ _ _ _.

(0,2), converted into standard formula x2+(y-2)2=0.

5。 Given the straight line Y+2=-X- 1, the slope of the point passing through _ _ _ _ _ _ _ _ _ _ _ _.

Organized into a standard formula: x+y+3=0. The slope is 1. Intersections can be written arbitrarily, such as (0, -3), (-3, 0).

6。 If the straight line AX+2Y+6=0 is perpendicular to the straight line x+a (a+1) y+(a2-1) = 0, then the value of a is _ _ _ _ _ _ _ _.

0 or -3/2, when A=0, the two straight lines are parallel to the X axis and the Y axis respectively, which meets the requirements. When a is not 0, the vertical slope is multiplied by-1, and A=-3/2.

7。 The equation of a circle with the point (2 1) as the center and tangent to the straight line 3X-4Y+5=0 is _ _ _ _ _ _ _.

(x-2) 2+(y-1) 2 = (12/5) 2. The distance from a point (2 1) to a straight line is12/5 (according to the formula), which is the radius.

8。 When the population consists of several obviously different parts, what is the best way to sample _ _ _ _ _ _ _?

group sampling

9。 When the intersection of the straight line 2X-3Y+6=0 and the X axis is A, the intersection of the straight line 2X-3Y+6 and the Y axis is B, and O is the coordinate origin, the area of the triangle AOB is _ _ _ _ _ _ _ _ _.

3。 A (3,0), B (0,2), AO=3, BO=2, AOB is a right triangle.

10。 Given a given point A (1, 0) B (-5, 0), find the equation of the vertical line in AB.

X+2 = 0. The midpoint of AB (-2,0), AB is on the X axis, and the perpendicular is parallel to the Y axis.

1 1。 The straight line L is on the X-axis and Y-axis, and the intercepts are a and b respectively. Find the slope of l (by the way, what is the slope).

B/a. Slope, that is, the degree of inclination. Tan value is defined as dip angle. One of the methods to find the slope described in this question. The coefficient of x can be divided by the coefficient of y, and the slope can be obtained from the analytical formula.

(This concept is basic and important. It is recommended to read more books and have a deep understanding. )

12。 AX+BY+C=0, and M(AX+BY+C)=0 means _ _ _ _ _ straight line (M≠0).

The same article. (Basic concepts, important)

13。 The positional relationship between 2X+Y-A=0 and X-2Y+B=0 is _ _ _ _ _.

Vertical, slope times-1

14。 Find the linear equation passing through a (-4,3) and B(2,-1).

2x+3y- 1 = 0。 Two-point formula: (x-2)/6=-(y+ 1)/4, simplified.

15。 In the program block diagram, there is a unique symbol _ _ _ _ _ _ _ with multiple exit points.

Referee box

16。 X+Y= 1，X2+Y2-2AY = 0(A & gt； 0) If there is nothing in common, find the range of A. ..

The second formula is a circle, X2+(Y-A)2=A2, center (0, a) and radius a ... It is easy to draw. If the circle crosses a point (0,0) and does not intersect with the straight line, it must be "hidden" under the straight line. A make a circle tangent to a straight line at most. Next, let's find the value of a in this critical case. (Please draw a picture to understand)

Note that the intersection of the straight line and the X axis is D, the center of the circle is O, the coordinate origin is B, and the tangent point is C.

Then OB=OC=A, BD= 1.

From the slope of the straight line, ∠ CDO = 45, so OD = ∠ 2 * a.

Therefore, a (1+2) =1.

A=√2- 1

Therefore, 0 < a < 2-1

17。 Find the length of the line X+ (root number 3)Y-2=0 cut by the square of the circle (x-2)+y2 =1_ _ _.

The radius of the circle is 1 and the center of the circle is (2,0); The center of the circle is on a straight line, so the line segment is the diameter of the circle and the length is 2.

18。 Find the distance between the coordinates of two intersections of X-Y+2=0 and X2+Y2=25.

Judging from the meaning of the question, the (x, y) that meets the requirements conforms to two equations.

Therefore, we bring into the cyclic equation: x2+(x+2)2=25 y=x+2, which is arranged as follows:

2x2+4x-2 1=0，

According to David's formula: x 1+x2 =-2, x 1 * x2 =-2 1/2.

Therefore, (x 1-x2)2=46.

Therefore, X-Y+2=0 on a straight line.

The distance is √2*(x 1-x2)=2√23.

19。 Write a program statement of1+1/2+1/3+…+1/0.

In what language?

30。 Draw a histogram of frequency distribution

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