A math problem for the second year of junior high school, can you help?

Connect BC to prove that DBC is equal to EBC, according to both sides and the angle!

Two thirds. Do the straight line y=x, the part enclosed by the rectangular border above the straight line is the part of the abscissa less than the ordinate The area of this trapezoid is 4 The total area is 6, so the probability is two-thirds.

Two thirds. With linear programming, make a rectangle in the coordinates, let the coordinates be (x, y) (x y), that is to say, x-y 0, make a straight line x-y 0, then the line above the line conforms to x-y 0 (excluding the line itself), the part that meets the intersection of the part and the rectangle is the requirement in the problem, the area is 4, the area of the rectangle is 6, then the probability is four-sixths, that is, two-thirds.

Math symbols are not easy to type, and it took me a long time to write these words.

Draw the figure first, four points form a rectangle, do the auxiliary line y=x, divide the rectangle into two halves, then any point of the upper half of y=x satisfies the topic, and the probability is the ratio of the area of the upper half of y=x to the area of the whole rectangle, that is, 2 3

Solution: The original formula can be reduced to: 2+9+2*3 under the root number 2, that is, under the root number (3 + root number 2) 2

i.e. 3 + root number 2

So the formula is =3 + 2+1 (2-1) = 4+2*2

Can't see clearly, huh? Write the above self-description.

Root number (11-6 root number 2) = 3 - root number 2

So the integer part is 1, then the decimal part is 2-root number 2

So x+y+2 y=3-root2+2 2-root2=1-2root2

Root number (3 - root number 2) 2 = 3 - root number 2

Sorry, I can't see the back clearly. Please write about the text part.

There is no way to copy it with a formulator.

You just look at it like this.

Original = (3 - root number 2).

Final result = 5

(1) There is a line segment on the map that has not changed the distance, that section is the time he stays 1h B is the top point, the left of the point is the image when he goes, the right is the image of his return, the distance is 60, and it takes 2 hours.

so his speed is 30kmh

I'm sorry, landlord, I won't be able to do the ones below. I'm stupid, hehe.

The first few questions are really simple, so let's do it yourself. Question 3: Draw Xiao Wang's functional relationship on that diagram, and then see how many intersections there are to meet a few times.

This is very simple, you didn't read the question carefully! -25 as you say....It started with (2100 x 3600), right? If you look at the previous equation (x-1600) x10%-25, this formula is x-1600!

But x is greater than 2100, so the part between 1600 and 2100 should be taxed at 5%! That is, 500x5%=25, so subtract the tax money in this range.

(1) AB=AC, P is the midpoint, so AP is perpendicular to BC, that is, angle APF + angle FPC = 90 degrees = angle APF + angle APE

Angle APE = Angle FPC, Angle PAE = Angle PCF = 45 degrees, AP=AC, so the triangle APE is all equal to the triangle PCF

Then ep=pf, the triangle epf is an isosceles right triangle (2) is known by the congruence relation in (1), ae=fc, so ae+af=ab=2cm triangle abp and triangle apc congruence, ab, ac side height is also equal, is 1cm triangle ape area is 1cm*ae*1 2, triangle apf area is 1cm*af*1 2

The area of the quadrilateral AEPF is 1cm * (ae + af) * 1 2 = 1 square centimeter Another: upstairs is too joyful.

Untie...

Because bac=120°. ba=ac

So b=30°= c

Because b=30°ad bc (3 wires in one), ab=2ad. (the nature of a right triangle of 30°).

Because bad=1 2=60° (3 wires in one) because aed=90°, ae=1 2ad

Because ab=2ad, ae=1 2ad, be=2-1 2ad=2 3ad

Therefore, AE is omitted from the proof step of some right angles compared to eb=1 2ad:3 2ad=1:3, I hope you can read it

bac=120° and ab=ac

ABC is an isosceles triangle.

D is the midpoint of BC.

ad bc bad= cad=60°(three-in-one) b=30°

Let the ad length be 1

de⊥ab∠aed=90°

ae=again ab=2

ae:eb=:(:3

Do CD axisymmetric B

Connect B'a The shortest line between two points is the shortest.

Look at the picture. <>

The principle of use is: the triangle is two sides and always greater than the third side.

There are the shortest paths of 8 and 15 squares of the square, i.e. 17.

Therefore, use the minimum cost: f=15*3000=45000.