Mathematical application problems (equations) (write the process clearly) The father is 38 years old and the son is 10 years old. A few years later, the father's age is three times that of the son?

X years later
38+x=3(10+x)
38+x=30+3x
3x-x=38-30
2x=8
x=4
A: four years later

Party A and Party B set out from ab at the same time and walk in opposite directions. Party A travels 8 kilometers per hour, and Party B travels 6 kilometers per hour. They meet at 3000 meters from the midpoint of ab

It should be
Let the distance be X
The distance of a is x / 2 + 3, and that of B is x / 2-3
Two people walk for the same time
（X/2+3）/8=(X/2-3)/6
The solution is x = 42

How to calculate 1.25 times 67.875 + 25 times 33.9375 + 1250 times 0.053375

1.25*67.875+25*33.9375+1250*0.053375
=8*1.25*67.875/8+4*25*33.9375+8*0.1250*10000*0.053375/8
=

The side length of equilateral triangle ABC is 4, ad is the middle line on the BC side, M is the moving point on ad, e is a point on the AC side, AE = 2, the minimum value of EM + cm is?

When points B, m and E are on a straight line, EM + cm is the shortest, and EM + cm = EM + BM = be = ad = 4 × (√ 3 / 2) = 2 √ 3

If the determinant D can't be mentioned, I'll write the fourth order, [] A1B1 A1B2 a1b3 a1b4.a1b2
If the determinant D can't be mentioned, I'll write it as fourth order, [] A1B1 A1B2 a1b3 a1b4.a1b2 a2b2 a2b3 a2b4 a1b3 a2b3 a3b3 a3b4 a1b4 a2b4 a3b4 a4b4]

I just answered the question
In the first column, A1 and the first column are added to the second, third and fourth columns by multiplying - A2, - A3 and - A4 respectively
D=a1*
b1 a1b2-a2b1 a1b3-a3b1 a1b4-a4b1
b2 0 a2b3-a3b2 a2b4-a4b2
b3 0 0 a3b4-a4b3
b4 0 0 0
= a1*(-1)^t(2341)*b4(a1b2-a2b1)(a2b3-a3b2)(a3b4-a4b3)
= -a1b4(a1b2-a2b1)(a2b3-a3b2)(a3b4-a4b3).

Prove by row and column that the area of the triangle whose midpoint is the vertex is equal to one fourth of the area of the original triangle`

Let (x1, Y1), (X2, Y2), (X3, Y3) area s = (1 / 2) × determinant 1,1,1x1, X2, x3y1, Y2, Y3. In the area s of midpoint triangle = (1 / 2) × determinant 1,1,1 (x1 + x2) / 2, (x2 + x3) / 2, (X3 + x1) / 2, (Y1 + Y2) / 2, (Y2 + Y3) / 2, (Y3 + Y1) / 2, = (...)

Let f (x) = {lgx (x > 0) 10 ^ x (x ≤ 0), then f [f (- 2)]=

f(-2)= 10^-2=0.01
f[f(-2)]=f(0.01)= lg0.01=-2

Calculation: (4m-n) (3m + 2n)

（4m-n)（3m+2n)
=12m²-3mn+8mn-2n²
=12m²+5mn-2n²

If three real numbers a, B and C form an arithmetic sequence with non-zero tolerance, and a, C and B form an arithmetic sequence, then the value of AB is zero______ ．

From the meaning of the question, we can get 2B = a + C, C2 = AB, ■ (2b-a) 2 = AB, ■ 4b2-5ab + A2 = 0, ■ 4-5 · AB + (AB) 2 = 0, the solution is ab = 4, or AB = 1, when AB = 1, the tolerance is 0, so the answer is: 4

There is a triangular open space in the shape shown in the figure on Zhongshan North Road under construction, which needs greening. Starting from point a, we plan to divide △ ABC into three triangles with equal area, so as to plant three different kinds of flowers and plants. Please help us to plan the pattern

Mathematical application problems (equations) (write the process clearly) The father is 38 years old and the son is 10 years old. A few years later, the father's age is three times that of the son?