Math Questions: Two questions for questions 7 and 8, and 8 questions for math questions

7.Through C to do the extension of BC, cross AD with point E, AC=10, CE:EA=1:

3, so CE:AC=1:2,EA:

ac= 3:2, so, ce=10 2=5m, ea=10 3=10 3, ea=10 3 3m, so be= (ab2-ea 2), bc=be-ce

I can't see clearly, just use I, pass A to do the BC perpendicular line, cross BC at the point F, the angle B is equal to 60 degrees, AB=6, so AF=3 3, BF=3, so DE=AF=3 3, I know, therefore, EC can be found, and the area is naturally found.

No one answered for a long time, so I'll do it.

1. Extend BC to cross AD and point E

It is known that bea=90° because the slope ratio is 1:3 and ac=10 m, so ce=5 ae=5 3 m.

It is known that ab=14m, ae=5, 3m, and get be=11mbc=be-ce=11-5=6m.

2. Make af bc at point f

It is known that b=60° ab=6 gives bf=3 af=3 3. af=de=3√3

Because i=1: 3, so ec=de* 3 =9 because ad=fe , we get bc=bf+fe+ec=3+4+9=16s=(ad+bc) de 2

The square is the cubic meter, 24d =, then, first calculate the volume of a square log: the bottom area is high, 500 square trees = 500

24dm=

3*A: There are 360 square meters of wood.

7. Proof:

ad bisects bac,de ab,df ac de=df

In RT DEB and RT DFC.

de=dfdb=dc

deb≌△dfc(hl)

be=cf8, may it help you!

It is enough to prove the congruence of two triangles, ad is the bisector of the angle, de, df are perpendicular to both sides of the angle, so de=df, and by db=dc, two right angle conditions, the congruence can be proved, and then the two sides are equal.

Question 7:

Solve the equation to obtain: x=50

Question 8: The first lock, you need to try 4 times.

The second lock needs to be tried 3 times.

The third lock needs to be tried twice.

The 4th lock needs to be tried 2 times.

The 5th lock needs to be tried 0 times.

4 + 3 + 2 + 1 + 0 = 10 times.

(87-78)÷(

9 = 50 (person).

Question 8 (1st lock) is opened with a maximum of 4 keys, 4 times.

2……3……Try 3 times.

Total: Up to 10 times.

<> I'm glad to answer the questions for you.

<> Sen Qingcheng, this seepage is like shouting stuffy pictures.

You just need to know how many elements a has, and the number of non-empty true subsets of a = 2 n -2

The numerator is 3, so the denominator can only be 1,3,-1,-3

So x has four, so the number of true subsets is 16-2=14

8。(4 5) Divide the closed culture by the shed guess (2 3).

4 Chain type 5)x(3 2)] divided by [(2 3)x(3 2)].

4/5)x(3/2)