Simple math problems in the second year of junior high school. Mathematics problems in the second ye

ab=ad angleABC=angleADC be=dc abe and adc congruence i.e., ae=ac angle aeb = angle acd angle aeb = angle ace + angle cae

Angular ACD = Angular ACE + Angular DCB

Angular cae = angular DCB

Angular AEC = Angular ACB

The complementary angle of the angle CAE = 2 angle ACB that is, the complementary angle of the angle DCB = 2 angle ACB

1.(2x+1) (x+2)(x+3)=a (x+2)+b (x+3).

On the right, we get (a*(x+3)+b*(x+2)) x+2)(x+3), i.e. ((a+b)*x+3a+2b) (x+2)(x+3) When x is not equal to -2 or -3, there is (a+b)*x+3a+2b=2x+1, so there is a+b=2, 3a+2b=1

So a=3, b=5

3.It can be seen that after A and B have done it together for 20 days, B will do it separately for 20 days.

A and B do it together for one day with an efficiency of 1 24 and do it for 20 days.

So B does 1 6 in the remaining 20 days, and B's work efficiency is 1 120, and A's work efficiency goes from 1 24 to 1 120 = 1 30

Therefore, it takes 120 days for B to complete alone, and 30 days for A to complete alone.

A needs x million yuan to work a day, and B needs y million yuan.

There are 24*(x+y)=120, 20*x+40*y=110 to get x=, y=

ps.Question 2: I don't understand what you're writing.

Side length = 16 4 = 4

High = 8 4 = 2

The degrees of the four inner angles of the diamond are 30 °, 150 °, 30 ° 150 °

16/4=4

sina=1/2

a=30°a=150°

The degrees of the four inner angles are 30°30°150°150°

The side length of the rhombus = 16 4 = 4

High = 8 4 = 2

According to the right triangle angle of 30 degrees, the opposite right angle is half of the hypotenuse, and the two acute angles are 30 degrees, and the obtuse angle is 150 degrees.

Satisfied?

Solution: Let the diamond shape be ABCD

Make de ab at point e

The rhombus has a circumference of 16

ab=ad=4

The rhombic area is 8

de*ab=8

de=4∠a=30°

c=30°，∠b=∠d=150°

Make the height of the other from one vertex, so that the height is 2, and then the outer angle of the height is 30 degrees.

So, the inner angles of the diamond are 30 degrees, 150 degrees, 30 degrees, and 150 degrees.

Solution: pd=ad-ap=10-x

i.e. y=10-x(0 x 10).

s△pcd=pd×dc/2=（10-x）×4/2=20-2x（0≤x＜10）

I don't understand, please ask, I wish you a happy o(o

1.18 root No. 3

3.Omitted 4If y=2x-3 (the question ms is wrong), it is 3 2

Let the time be x, according to the physical formula, v=v1+at, v is the final velocity, v1 is the initial velocity, a is the acceleration, and t is the time.

From the meaning of the title, we can see that the acceleration is ( 0·5-0) 1=, so 6=0+, and the solution is x=12s

Known: v=

Solution: t 12s

A: After 12 seconds it has a speed of more than 6m s.