Solving problems with one variable inequality (28 19:37:46) Supermarket a and supermarket B sell the same goods at the same price. In order to attract customers, they offer different preferential schemes: after supermarket a has purchased more than 300 yuan, the excess part will be given a 20% discount at the original price; after supermarket B has purchased more than 200 yuan, the excess part will be given a 50% discount at the original price. Suppose that customers expect to purchase X Yuan in total. (x > 300) (1) Please use the algebraic formula containing x to represent the expenses paid by customers in two supermarkets; (2) Try to compare which supermarket is more favorable for customers? Explain your reasons

Solving problems with one variable inequality (28 19:37:46) Supermarket a and supermarket B sell the same goods at the same price. In order to attract customers, they offer different preferential schemes: after supermarket a has purchased more than 300 yuan, the excess part will be given a 20% discount at the original price; after supermarket B has purchased more than 200 yuan, the excess part will be given a 50% discount at the original price. Suppose that customers expect to purchase X Yuan in total. (x > 300) (1) Please use the algebraic formula containing x to represent the expenses paid by customers in two supermarkets; (2) Try to compare which supermarket is more favorable for customers? Explain your reasons

(1) Store a: 300 + (x-300) * 80%; store B: 200 + (X-200) * 85% (2): 300 + (x-300) * 80% = 200 + (X-200) * 85% 300 + 0.8x-240 = 200 + 0.85x-17060 + 0.8x = 30 + 0.85xx = 30 / 0.05 = 600 yuan. It can be seen from this formula that when the shopping is less than 600 yuan, store B offers a discount, when it is more than 600 yuan

What is the law of 1 corresponding to 7, 2 corresponding to 19, 3 corresponding to 37

First of all, I wish you a happy New Year's day, and then I will answer for you
The law is y = (2n) ^ 2 + 3. The corresponding is 7 = (2 * 1) ^ 2 + 3, 19 = (2 * 2) ^ 2 + 3, 37 = (3 * 2) ^ 2 + 3, and so on
Thank you for reminding me downstairs. I'm sorry for my miscalculation
The rule is really y = 3N * (n + 1) + 1

2. 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61 Q: these numbers need to be arranged in addition to the multiples of three
2. 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61 Q: in addition to the multiples of three, what multiples should be excluded?
Numbers above 1

5 7 11 13 but the landlord gives all prime numbers

Use the problem to solve the equation and list 1-3 processes
1. There are 7 white balls and 24 yellow balls in the bag. The ratio of white balls in the key bag to the number of barren hills is 5:3. How many more white balls need to be added?
Solving equation 1.8 / 1.2 = x / (x-3)

Let's add x white balls
7+X：24=5：3
3（7+X)=120
7+X=40
X=33
You need to add 33 white balls
1.8/1.2=X/（X-3）
1.2X=1.8(X-3)
1.2X=1.8X-5.4
1.2X-1.8X=-5.4
0.6X=5.4
X=5.4/0.6
X=9

1. The number of real roots of the equation log (& frac12;) x = 2x (x is above 2). 2. The function y = log (a) x has / Y / > 1 on [2, + ∞), then
1. What is the number of real roots of the equation log (& frac12;) x = 2x (x is above 2)
2. If the function y = log (a) x has / Y / > 1 on [2, + ∞), what is the value range of a

1. Drawing method
1-1 first draw the function image of y = log (1 / 2) X
1-2 and then draw the function image of y = 2 ^ X
It is easy to know that there is only one intersection point between two function images, so the equation has only one real root
2. When 01
log(a)2>1=log(2)2 ,1

Del is the () key, press this key, the calculator will clear the current display of numbers and symbols; in the implementation of the second function key task, should first press the () key
dizzy,

This is a mathematical problem, science calculator is like this, ordinary calculator does not have these functions
Del is the (delete) key, press this key, the calculator will clear the current display of numbers and symbols; in the implementation of the second function key task, should first press the (2ndf) key

Rtotal = (R1 + R2) / r1r2 what does rtotal mean? What do R1 and R2 mean?

R is always the total resistance of the parallel circuit, R1, R2, R3 Is the resistance value of the divider

In the expansion of (x-1 / x) ^ 5, the binomial coefficient with x ^ 3 term is?

5

Now we define two operations "+" * ", any two integers a, B.A + B = a + B-1, a * b = AB-1, calculate the value of 4 * [(6 + 8)) * (3 + 5)]
Give me more points!

6+8=6+8-1=13
3+5=3+5-1=7
13*7=13×7-1=90
4*90=4×90-1=359

When the coefficient of the first term is 0, the quadratic equation of one variable always has real roots which are not equal to 0
If the constant term of quadratic equation of one variable is 0, then 0 must be one of its roots
Which of these two sentences is wrong? Tell me the reason

When the coefficient of the first term is 0, the quadratic equation of one variable always has real roots which are not equal to 0
This is wrong
For example, X & sup2; + 1 = 0
There is no real root