There is an English book on the teacher's desk

There is an English book on the teacher's desk

There is an English book on the teacher's desk.

The number of people in class 6.2 is nine tenths of that in class 6.1. There are five less people in class 6.2 than in class 6.1. How many people are there in class 6.1?

50 people
If the number of class 6.1 is x, the number of class 6.2 is 9x / 10
According to the meaning: x-9x / 10 = 5, x = 50
There are 50 people in class 6.1

The polynomial a ^ 2 x ^ 3 + ax ^ 3-4x ^ 3 + 2x ^ 2 + X + 1 is a quadratic polynomial about X. find the value of a ^ 2 + 1 + a

5
Because it is a polynomial of degree 2, the coefficient term of x ^ 3 is 0
that is
a^2+a-4=0

Alcohol and water of the same quality (ρ alcohol < ρ water) are poured into containers with the same bottom area but the shape as shown in the figure. Alcohol is poured into container a, and water is poured into container B. then the pressure of liquid on the bottom of container P A and P B is ()
A. P a > P B. p a = P B C. p a < P B D

When alcohol is poured into container a, the pressure of alcohol on the bottom of the container is equal to the gravity of alcohol; when water is poured into container B, the pressure of water on the bottom of the container is greater than the gravity of liquid, because the bottom areas of the two containers are the same; according to the formula P = FS, the pressure of alcohol on the bottom of the container is less than that of water on the bottom of the container

Simplified evaluation (m square-n Square) square / (m square-2mn + n square) - (m square + n square) where [M square + n square-8] + (m-n-1) square = 0
Note: [] is absolute value symbol!

Because of the fact that m-n-n-1 (m-n-1) is the result of M & \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\(m-178; - 2Mn + n-178;)

Simple calculation method (1-1 / ^ 2) (1-1 / ^ 3) (1-1 / ^ 4) （1-1/^9)(1-1/^10)
The above questions are invalid
Right
A simple method to calculate 3 * (a-2b) (1 / 3 * a + 2 / 3 * b)

Incomplete expression of the title

Four fifths multiplied by nine seven plus four fifths multiplied by two nines, how can it be simplified

Original formula = 4 / 5 times (7 / 9 + 2 / 9) = 4 / 5

(2005 + 2003 / 1) * how to calculate 2004 / 1?

2005=2004+1
2003=2004-1
The original formula = (2004 + 1 + 2004-1) / 2004 = 2

Operation law and simple operation
A box of apples is 8 yuan cheaper than a box of grapes. 4 boxes of apples is 220 yuan. How much does a box of grapes cost? Use the recursive equation to calculate!

Grape = 220 △ 4 + 8 = 63 yuan

76 * 237 + 327 * 24 calculated by simple method

(76+24)*237+（327-237）*24=100*237+90*24=23700+2160=25860