Mathematics in life, help, I m really anxious

What math is in life?

Electricity fee when the sub-tariff is implemented: RMB.

Electricity charge when the sub-tariff is not implemented: RMB.

Yuan answer: When the sub-price is not implemented, the electricity cost is greater, and it is more yuan.

Equal difference, a1 + a3 = 2a2

s3=a1+a2+a3=3a2=12

a2=4, then a1=4-d, a3=4+d

In equal proportions, a2 = 2a1 (a3 + 1).

16=2(4-d)(4+d+1)

d²+d-12=0

d=-4,d=3

d=-4，a1=8

an=-4n+12

sn=(8-4n+12)n/2=-2n²+10nd=3a1=1

an=3n-2

sn=(1+3n-2)n2=(3n -n) 2, so sn=-2n+10n, or (3n-n)2

1.The main test is the Pythagorean theorem, where the height of the hypotenuse is multiplied by the hypotenuse = the product of two right-angled edges.

2.If the short right-angled edge is x, then the long right-angled edge is 3x. Using the Pythagorean theorem to figure out the right-angled edge, the area comes out.

3.You can draw a picture on scratch paper, and their shape is a right triangle. The distance is hypotenuse.

I didn't write the answer just to tell you that the idea is to hope that you do it yourself.,So that you can have a better improvement.,If there's anything you don't understand, you can ask me.。。

1. According to the Pythagorean theorem, the square of the length of the hypotenuse is equal to a2+b2 that is, 52+122 so the hypotenuse is 13 because the area of the triangle is 12*5 2 so the area of the triangle is 30 so the height on the hypotenuse * hypotenuse = 30 * 2 = 60 so the height on the hypotenuse is 60 13

2. One third of another right-angled side, let the length of this side be x, then a right-angled side is 3x (the purpose of this setting is for calculation convenience).

Then from the Pythagorean theorem: x 2 + 9x 2 = 100x 2 = 10

The area of the triangle is: 1 2*3x 2=15

3. According to the Pythagorean theorem, sailing to the east is perpendicular to sailing to the south, and at 10 o'clock in the morning, each exercised 8*2=16 nautical miles to the east and 12*1=12 nautical miles to the south, so there are 12 2 + 16 2 = 400, and the opening number is 20 nautical miles.

1.First, find the slope height as 13. Multiplying 5 by 12 and dividing by 13 equals 60/13.

2. If one side is x, then the other side is 3x.

The square of the column equation (3x) + the square of x = the square of 10.

Find x. Multiply x x by 3x and divide by 2 to choose b

3. By 10 a.m., the first boat had traveled for 2 hours, 2 times 8 = 16 nautical miles.

Another small boat traveled 1 hour and 12 nautical miles.

They form a right triangle, so they are separated (16 squared plus 12 squared) and then squared = 20 nautical miles choose d

1。The hypotenuse is 13 long, so the height is 60 13

2。Let one right-angled edge be x, then the other is 3x, x + (3x) = 10, so x1*x2 = 30, so the area is 15

3。The answer is d

Set the percentage of the price reduction to be x

200(1-x) 2=128 gives x=20

Set the percentage of the price reduction to be x

200 (1-x) 2 = 128 and the rest will be counted by yourself.

Divide 200 by 128 and then subtract one to get the number of percentages.

As shown in the figure below, the answer to the multiple-choice question is to be adopted.

Qing: I'll just tell you the first two, do you say yes or no?