A few math questions in the second year of high school, urgent

1.a>=0 from the title

x +√y >=2√√x y==0 a^2(√x -√y)^2+(2a^2-4)√x y>=0

2a 2-4>=0 gives a>= 2

px-6 x -x+1<6 gives [-3x 2+(p+6)x-12] x -x+1<0 because the denominator <0 denominator Evergrande is 0 numerator <0 similarly find the set of "-9" and then find the intersection.

0 and the odd function f(x) is a subtraction function defined on [-1,1].

f(a²-a-1)>f(-4a+5)

a²-a-1<-4a+5……①1≤a²-a-1≤1……②1≤4a-54a-51……③

Then find out. 4.Let the length x width of the vegetable planting area y (x+2)(y+4)=800 xy=x(800 (x+2)-4)=800x (x+2)-4x=[800(x+2)-1600] (x+2)-4(x+2)+8=808-1600 (x+2)-4(x+2) 808-160=648 (basic inequality).

I can do both the third and fourth questions, but I write them on paper, and the first and second questions need to use the mean inequality, good luck.

I think I'm pretty good at math, but I can't understand your question at all.

From "the midpoint of the line segment happens to be the coordinate origin", the equation for the line l can be set as: y=kx;

Coupled with the above two straight lines, you can get two intersection coordinates (this is up to you, let's assume that (x1, y1); (x2，y2));

Then the midpoint formula is obtained: (x1+x2)=0; (y1+y2)=0 to solve the k value and get the equation for the straight line l.

From the meaning of the question to know the origin of the coordinates, it can be assumed that l:

y=kx let the intersection of l and the straight line 4x+y+6=0 be (x1

y1）;The intersection point of l and the straight line 3x-5y-6=0 is (x2,y2).

The simultaneous solution of the equation yields x1=-6 (4+k) and x2=6 (3-5k).

Because x1+x2=0

So we can find k = -1 6 .

From the meaning of the title, abb1a1 and bb1c1c are all squares, and they are all perpendicular to the bottom abc.

B is the coordinate origin, BA is the X-axis, BC is the Y-axis, and BB1 is the Z-axis.

Then a1(a,0,a),a(a,0,0),c(0,a,0) so the vector ba1=(a,0,a),ac=(-a,a,0) so the drain cosine cos cos = ba1*ac |ba1|*|ac|=-1 2 Therefore, the angle is 60 degrees (take the complementary angle of 120).

1、b

Analysis] Using similar triangles, the correspondence becomes proportional and easy to know

Pa (Pa+AC)=ab cd Therefore: cd=203, parallel or in the plane.

4. Innumerable, one, one [the above answer is wrong].

5. [The counter-proof method is a commonly used method when proving solid geometry] assumes that the straight line b is not parallel to the plane, and :b

must intersect with the surface, you may wish to set the intersection point as m, the straight line a plane, you can pass m to make the straight line c, so that c a and a b, and b, c over the same point m, can only b, c coincide, and contradict the question.

then the assumption is not true, the straight line b plane

1。 b⊥β

2。Insufficient conditions.

3。or a contained

4。Countless perpendiculars. 1 vertical face, countless vertical faces.

5。Counter-proof, assuming that the line b is not parallel to the plane, then it intersects with the plane, and the intersection point is m, because the line a plane , then the line c can be made through m, so that c a

At the same time, a b, and b, c pass the same point m, so only b, c coincide, and the contradiction with the question is not true, the straight line b plane

1.Suppose the unit price of the first fruit is 10 yuan, and the unit price of the second time is 100 yuan

A bought a total of 40,000 catties, a total of 200,000 + 2 million = 2.2 million B bought a total of 40,000 yuan, the first time he bought 2,000 catties, the second time he bought 200 catties, a total of 2,200 catties.

A (unit price): 2,200,000 40,000 = 110 2 = 1210 22B (unit price): 40,000 2,200 = 400 22 = 400 22 It can be seen that B's purchase method is more cost-effective.

The second question has not been done like this in a long time, no.

3.I feel that the ratio of the distance from point P to MN is a useless condition.

Point n is the center of the circle, draw a circle with a radius of 1.

The distance from the point n to the straight line pm is 1, so the straight line pm must be the tangent of this circle.

Since mn=2 and radius 1, the distance from the tangent point to m is 3

There are two possible points of this kind, one is (1 2, 3 2) and the other is (1 2, - 3 2).

So the answer is also 2, one straight line passes through (-1,0)(1 2, 3 2) and the other straight passes through (-1,0) (1 2,- 3 2) from which 2 straight lines are obtained.

y1=(√3/3)x1 + 3/3

y2=(-√3/3)x2 - 3/3

1 All 1) Treat A and B as a whole, and there are 2 ways to stand in themselves, and then see it as a full arrangement of 4 people, shared.

4 3 2 1 2 = 48 species.

2) There are 6 kinds of 3 people except A and B, and then 2 positions are taken between 3 people and a total of 4 positions at both ends to A and B, and there are 12 types, a total of 6 12 = 72 kinds.

or use the full arrangement of 5 people 120 kinds minus the adjacent station method 48 kinds = 72 kinds 3) in three steps: the remaining 3 people all arrange 6 types; A has 3 positions except for the left end, and there can be 3 kinds of rows; There are 4 types in the last row B. There are 6 3 4 = 72 species.

（1）a22*a44=48

2）a33*a24=72

3) There is a method in A55 in the full arrangement, remove A33 on the left and B on the right, remove 2C13*A33 on the left side of A and B on the right side of B that is not left on the right, A55-A33-2C13*A33 = 78

If A and B are adjacent, then according to A and B are one person, and there is an arrangement of 4, that is, 4*3*2*1=24, and because A and B can be transposed, there are a total of 24*2=48 kinds.

The full arrangement of 5*4*3*2*1=120 kinds, so the non-adjacent station method of A and B is 120-48=72 kinds.

3. There are 24 kinds at the left end of station A, 24 kinds at the right end of station B, and 6 kinds at the left end and at the right end. So there are 120-24-24+6=78 species.

a4 4 times a2 2

a5 5 minus "a4 4 times a2 2".

a5 5-2 multiplied by a4 4 + a3 3

1。I didn't get it.

b=,a b(a-b)= The question is incorrect.

times the root number 24The radius of the bottom circle is taken as 2 times the 3rd root (cm).

Take 4 times the height of the 3rd root (cm).

Hero, you don't need to put 4 wrong questions up, the wrong questions are also level, and the wrong questions like you are too low-level, who are you fooling?

1.(3x-6) 2 16-y 2=1 (y is not a mess scum 0) 2...The parabolic form is wrong 3 If the question is a regular triangle, answer 2

Let the coordinates of this point be p(x, crack finger y) then (-x, -y) + (6-x, -y) = (6-2x, -2y).

Point c coordinates 2 (6-2x, -2y) = (12-4x, -4y) substituting the hyperbolic equation to obtain.

12-4x) 2 16-16y 2 9=1 The second question is frankly wrong.

The product of the eccentricity of the three questions of the first Rangyuan Bridge is 1