One factor is 7, the other is 6, and the multiplication is

One factor is 7, the other is 6, and the multiplication is

7x6 = 42 or 6x7 = 42

If one factor is 8 and the highest order of the other factor is 7, what is the product of them
The last sentence is the number of digits of their product

One factor is 8,
The other factor is 7ab, with a maximum of 799 and a minimum of 700
799×8 = 6392
700×8 = 5600
So the product must be between 5600 and 6392, it must be four digits

It is easy to calculate the ratio of 7:8 + 88:7 + 888:7 + 8:1 × 3 and 10 △ 8 + 3.96 × 12.5% + 0.204 × 1:4

8 and 8 of 7 + 88 and 8 of 7 + 888 and 8 of 7 + 8 of 1 × 3 = 9-1 / 8 + 89-1 / 8 + 889-1 / 8 + 3 / 8 = 9 + 89 + 889 = 98710 △ 8 + 3.96 × 12.5% + 0.204 × 1 and 4 of 1 = 0.125 × 10 + 3.96 × 0.125 + 2.04 × 0.125 = 0.125 × (10 + 3.96 + 2.04) = 0.125 × 16 = 2

It is known that the complete set I is r, the set a = {X / 2 ^ X1}, and the set M = {X / X}

(2) Let I = R be a complete set, and let m = {x | y = (x square - x + 1) / [(a-5) * a square + X + X / 3-A be greater than 0. Take a = 4 and calculate the value

The purchase price and selling price of color TV sets are shown in the table below; (1) according to the national policy, farmers can enjoy 13% government subsidy when they buy "home appliances to the countryside". Farmer Tian Dabo goes to the shopping mall to buy a refrigerator and a color TV set. How much government subsidy can he enjoy? (2) in order to meet the needs of farmers, The shopping mall decided to purchase 40 color TV sets with no more than 8500 yuan, and the number of refrigerators is no less than five sixth of the number of color TV sets. What is the maximum profit of the shopping mall (profit = selling price purchase price), and what is the maximum profit; The purchase price of refrigerator is 2320 yuan, and the selling price is 2420 yuan. The purchase price of color TV is 1900 yuan, and the selling price is 1980 yuan
 

How much government subsidy do you enjoy
(2420 + 1980) * 13% = 572 yuan
Please help the mall design the corresponding scheme
We will purchase x refrigerators and (40-x) color TV sets
2320x+1900(40-x)=(40-x)*5/6
The solution is x = 18.18, that is 18.18

X-4y-x-2y (factorization)
process

The original formula = (x + 2Y) (x-2y) - (x + 2Y) = (x + 2Y) (x-2y-1)

1994+199.4+19.94+1.994=?199999+19999+1999+199+19=?
How to simplify the calculation?
Write out the main operation process

1994+199.4+19.94+1.994=1994(1+0.1+0.01+0.001)=1994*1.111=1.111(2000-6)=2222-6.666=2215.334¬199999+19999+1999+199+19=200000+20000+2000+200+20-5=222220-5=222215

This is a determinant?
2 1 -5 1
1 -3 0 -6
0 2 -1 2
1 4 -7 6

This determinant is symmetric
The specific measures are as follows:
Multiply the first row of the determinant by - 1 and add it to the other rows
After splitting into 2 determinants
One of them is the standard trigonometric determinant
Another one can put forward that after the first column, each column can be multiplied by a coefficient and added to the first column to become a triangular determinant
Two trigonometric determinants are easy to calculate
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-How to calculate 7 divided by 3-14 divided by 3

-7 divided by 3-14 divided by 3
=-(7 + 14) divided by 3
=-21 divided by 3
=-7

When x tends to 1, how to find the left and right limits of function ((x ^ 2-1) / (x-1)) e ^ 1 / (x-1)

Let X-1 = t, T -- > 0
lim (x-->+1)（(x^2-1)/(x-1))e^1/(x-1)
=(x-->+1)（(x+1)e^1/(x-1)
=lim (t-->+0)（t+2)e^1/t
=+∞
lim (x-->1-)（(x^2-1)/(x-1))e^1/(x-1)
=(x-->1-)（(x+1)e^1/(x-1)
=lim (t-->-0)（t+2)e^1/t
=0