1. 28 questions in junior high school mathematics, O O thank you

Seeking congruence? Try an extension cord or "truncating". Sorry, ** can't see clearly.

Is there a problem with this question?,I always feel like there's something missing.,I've been thinking about it for a while.。

Let me think again ...

Is there a problem with this question? It can be found that the angle CAD=30° should be the angle ACF=3 angle CAD

2x+3y=3m+7 (1)

x-y=4m+1 (2)

2)*3, 3x-3y=12m+3 (3)(1)+(3), 5x=15m+10

x=(15m+10)/5

x=3m+2

Substituting x=3m+2 into (2) obtains, 3m+2-y=4m+1-y=4m+1-3m-2

y=m-1y=1-m

Because the solution of the system of equations is a pair of positive numbers, the coefficients of x,y are greater than 0 so 3m+2>0 and 1-m>0, so m<1 and m>-3 2

i.e. -3 2|m-1|+|m+2/3|Medium, when -2 3 when -3 2When < m<-2 3, the original formula =-(m-1)-(m+2 3)=-2m+1 3< p>

The basic idea is to divide the big square into four right-angled triangles, and the level around the small square is not enough, and there is no way to insert **, so I have to write about it, you might as well mark and move 1 according to the following description, mark the midpoint of AG as m, mark the midpoint of EF as n, and connect mn, em, fm. Note that since the side length of the large square is twice that of the small square, en=fn=am=gm=small square side length.

2. Move the right-angled triangle enm so that en coincides with ed, nm coincides with dc, m falls on dc extension line, and cm=dc

3. Place other right-angled triangles in order according to the above ideas, so as to ensure that the long right-angled side of each right-angled triangle coincides with the short right-angled side of another right-angled triangle and one side of the small square.

I don't know if it's clear, after the level is enough, I'll send a note with **.

1.Let ab=xcm

1)x+1/2x=24 (2) x+1/2x=30x=16 x=20

ab=ac=16 bc=22 ab=ac=20 bc=142.(1)

a=602).

x=903. 3x-4≤6x-2

2/3≤x2x+1÷3-1＜x-1÷2

x 1 62 3 Kishan x 1 6 Because it is an integer, x=03(x+a)-5a+2=0

a=1 substitute a=1 into 5a's 7 cubic (?) Defeat is to the seventh power, right)-2a points of the fight withered in 1.

1.Let ab=xcm

1) x+1 2x=24 (2) x+1 2x=30x=16 x=20

30-1 Wang or Kai limb 2 16=22 24-1 2 20=14ab=ac=16 bc=22 ab=ac=20 bc=14

Serial: y = kx - 5

2x + 3k(kx - 5) =7

2 + 3k 2) x = 7 + 15k 2 + 3k 2 constant.

x = 7 + 15k) 2 + 3k 2) 0 i.e. 7 + 15k 0

Solution k 7 15

Column: x = 7 - 3ky) 2

k(7 - 3ky)/2 - y = 5

3k 2 2 + 1) y = 7k 2 - 5 3k 2 2 + 1 constant.

y = 7k/2 - 5 ＜ 0

Solution k 10 7

7/15 ＜ k ＜ 10/7

I haven't done it for a long time.,This method should be possible.,This number loses my head big.,Is there a miscalculation to see if it's called.

There is also the triangle high line, which is the line segment from one of the vertices of the triangle to the opposite side, and between the vertex and the perpendicular foot.

The high line of the triangle is the height of the triangle, and the high line is called the high line.

The high line is the height of the triangle.

1.Master Li brought his apprentice Xiao Wang on April 1 today, under the guidance of the master, the number of pieces produced by Xiao Wang increased by 2 pieces per day, and it is known that the master can produce 60 pieces per day, and Xiao Wang wants to catch up with the master in the first month. (1) Find the functional relationship between Xiao Wang's work efficiency v (piece day) and working time t (day); v=2t(2) to find the work efficiency of Xiao Wang on the 6th day; v=12(3) to find the first few days, Xiao Wang can produce 38 pieces per day; t=19(4)Can Xiao Wang's wish come true?

Yes, 30 days is exactly 60 pieces day 2Let x be the sales revenue of a certain commodity, and y is the gross profit obtained (gross profit = sales revenue - cost), if the gross profit margin (gross profit = gross profit cost) reaches 40%, then what is the functional relationship of y about x? y/(x-y)=40%y=

=4 3+12 3-4 3 7 Quadruple root number three plus twelve times root number three minus four-sevenths root number three.

108 3 7 108 times the root number 3.

One hundred and forty times the root number three.