Solution equation: 2 (x-1) + 3x = 13 3 (X-2) - 2 (x + 1) = 5

Solution equation: 2 (x-1) + 3x = 13 3 (X-2) - 2 (x + 1) = 5

2(x-1)+3x=13
2x-2+3x=13
2x+3x=13+2
5x=15
x=15÷5
x=3
3(x-2)-2(x+1)=5
3x-6-2x-2=5
3x-2x=5+6+2
x=13

The solution equation of X + 8 = 13

x=13-8
x=5

How to solve the equation x + 8 = 13

X+8=13
X+8－8=13 －8
X=5

Use the rounding method to approximate the following values according to the requirements in brackets:
(1) 486 (accurate to 0.01)
(2) 60590 (keep three significant numbers)
(3) 03057 (3 significant digits reserved)
(4) 2345000 (accurate to 10000 bits)

（1）28.486 0.01 28.49
（2）60590 6.05×10^4
（3）0.03057 0.0306
（4）2345000 2.35×10^6
That's it.

How long does it take for a 150m long train to run on a 600m long bridge from entering the tunnel entrance to its full passage

(600 + 150) / speed = time

The quadrilateral ABCD is a rectangle, the length BC and width CD are 6 cm and 4 cm respectively. The area of triangle EFD is 6 square cm larger than that of triangle ABF, and the length of ED is calculated

Area of rectangle ABCD:
4 × 6 = 24 (square centimeter);
Area of triangular EBC:
24 + 6 = 30 (cm2);
The length of Ce: 30 × 2 △ 6 = 10 (CM);
Length of de: 10-4 = 6 (CM)

Is light year the largest unit of length?

Light year is generally used in astronomy to measure a great distance, such as the distance between the solar system and another star. Light year is not a unit of time. Second gap is another commonly used unit in astronomy. One second gap is equal to 3.26 light years. A light year is about 63240 astronomical units

The charging standard of a local communication company is as follows: the first is: 25 yuan per month, 0.20 yuan per minute. The second is: no monthly fee, call fee per minute
25 yuan. (1) calculate how many minutes a month, the two standards pay the same call fee? (2) when the time is not reached, which is more affordable? (tell me quickly, I have something urgent, the teacher will talk about tomorrow, thank you, fast.)

Set the call minutes as X, the first tariff is 25 + 0.2x, and the second tariff is 0.25x
When the two rates are equal, that is, 25 + 0.2x = 0.25x, the solution is x = 500
So when the call time is 500 minutes a month, the two kinds of charges are the same. When the call time is less than 500 minutes, choose the second one

As shown in the figure, in square ABCD, DP is made through point D, AC is intersected at point m, AB is intersected at point n, and the extension line of CB is intersected at point P. the proof is: DM ^ = Mn * MP

Main points of proof: Method 1: connect BM, first use congruent proof ∠ ADM = ∠ ABM, DM = BM and ∠ ADM = ∠ P, so ∠ P = ABM, and because ∠ PMB = ∠ PMB, so △ PMB ∽ BMN, so MP / BM = BM / Mn, so MP / DM = DM / Mn, so DM ^ 2 = Mn * MP

How can the cubic power of DM be converted to the cubic power of M

Because 10dm = 1m
So 10 & # DM & # 179; = 1m & # 179;
That is, 1 DM & # 179; = 0.001 M & # 179;