If the image of a function is known to pass through points (1,1) and (2, - 1), the analytic expression of the function and the range of X which makes the value of the function positive are obtained

If the image of a function is known to pass through points (1,1) and (2, - 1), the analytic expression of the function and the range of X which makes the value of the function positive are obtained

Let the analytic expression of this linear function be y = KX + B. then the solution of 1 = K + B − 1 = 2K + B is k = − 2B = 3, and the analytic expression of the function is y = - 2x + 3. From the meaning of the problem, we get - 2x + 3 > 0, and x < 32, so the range of X with positive value is x < 32

Xiao Ming fills a cuboid glass container with a bottom of 30cm * 30cm with water, and pours part of the water into a cube iron bucket. When the cube iron bucket is filled with water, the sleep in the cuboid container drops by 20cm. Does the edge length of the cube iron bucket exceed 25cm?

It can be seen from the meaning of the title:
The volume of water poured from the cuboid container is:
V = 30 * 30 * 20 = 18000 cubic cm
The volume of a given cube is:
V = 25 * 25 * 25 = 15625 cubic cm
because
V>v
therefore
The edge length of the cube bucket is more than 25cm

In the triangle ABC, ab = AC, the angle BAC = 120 degrees, the triangle ade is an equilateral triangle, the point D is on the side of BC, BD: DC = 2:3, when the area of the triangle ABC is 100 square centimeters, the area of the triangle ade is calculated

Let the height of the triangle ABC = h and its base be BC
Triangle ABC area = 0.5 * h * BC = 100 square centimeters,
Therefore, BC = 200 / HCM
Suppose that E also falls on BC (it's easier to solve, because there is no explanation, e may also be outside the triangle), and De is the bottom of the triangle ade
When BD: DC = 2:3, BC = BD + DC = BD + 1.5, BD = 2.5 BD,
BD = BC / 2.5 = 200 / 2.5h = 80 / HCM
De = BC - 2 BD = 200 / h - 2 BD = 200 / h - 160 / h = 40 / h cm
Area of triangle ade = 0.5 * h * de = 20 cm2

5 ^ 2-3 ^ 2 = 8 × 29 ^ 2-7 ^ 2 = 8 × 4 15 ^ 2-3 ^ 2 = 8 × 27. What's the rule?

As follows: 16 ^ 2-4 ^ 2 = 8 * 30; 18 ^ 2-2 ^ 2 = 8 * 40
In fact, this is the square difference formula, that is, a ^ 2-B ^ 2 = (a-b) * (a + b). But if you have to multiply 8 by a certain number on the right side of the equal sign, you only need to calculate the number on the right side of the equal sign (which is a multiple of 8), and then calculate the number on the left side
If you want to explain the correctness of this rule, just open the brackets of (a-b) * (a + b) to a * a + A * B-A * B-B * B, and get a ^ 2-B ^ 2

If the first n terms of the equal ratio sequence {an} and Sn = 3N + R, then r = ()
A. 0B. -1C. 1D. 3

∵ Sn = 3N + R, sn-1 = 3n-1 + R, (n ≥ 2, n ∈ n +), ∵ an = sn-sn-1 = 2 · 3n-1, and A1 = S1 = 3 + R. from the general term, A2 = 6, common ratio is 3, ∵ A1 = 2, ∵ r = - 1

Primary school sixth grade math problem master to help me solve 10 points, thank you
It takes 10 hours for Party A to make a batch of parts. Party B can only make 6 / 5 (5 / 6) of this batch of parts in the same time. Now after Party A and Party B work together for 3 hours, Party A will do the rest. How many hours?
I hope I can answer it all in Chinese, add, subtract, multiply, divide, score, not clear with numbers and symbols

One plus five sixths of the sum multiplied by three equals five and a half hours
Ten minus five is four five

a+ab+abc+abcd=2002 a=?b=?c=?d=?

a=1
b=8
c=0
d=3

1 2 3 4 5 = 31, fill in the calculation symbol in the space

(1+2)*3*4-5=31

If the rank of a 3 × 3 matrix is less than 3, then the determinant of the matrix is equal to zero

The rank of the matrix is less than 3, which indicates that the simplest row ladder of the matrix has a behavior of all zero. According to the property of the determinant, we can know that the determinant is zero at this time and the form of upper triangle

Choose 9 numbers from 1.2.3.4.5.6.7.8.9.10 and fill in () to form three formulas. Each number can only be used once

1+4=5 2+6=8 3+7=10