2x △ 2.3 = 4.56 & nbsp; & nbsp; & nbsp; 7 (x - 1.2) = 2.1 (test) & nbsp; & nbsp; 0.7 (x + 0.9) = 42 & nbsp; & nbsp; & nbsp; & nbsp; 7x + 3 × 1.4x = 0.2 × 56 (X-9) △ 98-x-9) = 4

2x △ 2.3 = 4.56 & nbsp; & nbsp; & nbsp; 7 (x - 1.2) = 2.1 (test) & nbsp; & nbsp; 0.7 (x + 0.9) = 42 & nbsp; & nbsp; & nbsp; & nbsp; 7x + 3 × 1.4x = 0.2 × 56 (X-9) △ 98-x-9) = 4

（1）2x÷2.3=4.56，    2x÷2.3×2.3=4.56×2.3，              2x=10.488，        ...

Solution equation: 2 (x-3) (x + 1) = x + 1

2 (x-3) (x + 1) = x + 1, transfer term to get: 2 (x-3) (x + 1) - (x + 1) = 0, ■ (x + 1) [2 (x-3) - 1] = 0, sort out: (x + 1) (2x-7) = 0, ｜ x + 1 = 0 or 2x-7 = 0, ｜ X1 = - 1, X2 = 72

Finding the general solution of the equation x (1 + y ^ 2) DX + y (1 + x ^ 2) dy = 0

X (1 + y ^ 2) DX + y (1 + x ^ 2) dy = 0x (1 + y ^ 2) DX = - Y (1 + x ^ 2) dyxdx / (1 + x ^ 2) = - YDY / (1 + y ^ 2) DX ^ 2 / 2 (1 + x ^ 2) = - dy ^ 2 / (1 + y ^ 2) d (1 + x ^ 2) / 2 (1 + x ^ 2) = - D (1 + y ^ 2) / (1 + y ^ 2) ln (1 + x ^ 2) / 2 = - ln (1 + y ^ 2) / 2 + CLN (1 + x ^ 2) = - ln (1 + y ^ 2) + 2C. The general solution is ln (

Four rectangles, 12 long and 6 wide, and a small orthomorphic form a large square to calculate the area of a small square

The length and width of four small rectangles are relatively enclosed together to form a large square with length of 12 + 6 = 18. A small square with side length of 6 is formed in the middle of them, and the area of the small square is 6 * 6 = 36

There are three round pillars by the door of the school auditorium, with the bottom diameter of 0.8 meters and the height of 5 meters. How many square meters of painting area are there to repaint these three pillars
Tip: only the side of the cylinder needs to be brushed

What is the area to be painted for each column
0.8 × 3.14 × 5 = 12.56 (M2)
share
12.56 × 3 = 37.68 (M2)

How can five five skillfully use operation symbols equal to eight?

5＋5－（5＋5）÷5＝8

Let y = ∫ e ^ (x ^ 2) DT + 1 (integral upper limit is 2x, lower limit is 0), its inverse function is x = f (y), then how much is the second derivative of F (y)

Y = e ^ (x ^ 2) * (2x-0) + 1 = 2x * e ^ (x ^ 2) + 1 his inverse function expression x = 2Y * e ^ (y ^ 2) + 1x '= 2 * e ^ (y ^ 2) + 2Y * e ^ (y ^ 2) * 2Y = (2Y + 2) * e ^ (y ^ 2) x "= 2 * e ^ (y ^ 2) + (2Y + 2) * e ^ (y ^ 2) * (2Y) = (4Y ^ 2 + 4Y + 2) * e ^ (y ^ 2)

(1*1+2*2)/(1*2)+(2*2+3*3)/(2*3)+(3*3+4*4)/(3*4)+(4*4+5*5)/(4*5)+...+(2002*2002+2003*2003)
/(2002*2003)+(2003*2003+2004*2004)/2003*2004

[ n^2 +(n+1)^2] / [n*(n+1)] = (n+1)/n + n/(n+1)
= 2 + 1/n - 1/(n+1)
The original formula is 2 * 2003 + 1-1 / 2 + 1 / 2-1 / 3 +. + 1 / 2003-1 / 2004
= 4006 + 2003/2004

How to use addition, subtraction, multiplication and division to get 2008

The principle is to get closer as soon as possible
If you can combine them at will:
2222-2008=214
222-214=8
So 2222-222 + 2 * 2 * 2 + 2-2 is enough
If it can only appear in the form of a single 2, it is impossible, because the fastest way to reach 2008 is to multiply, and 2 ^ 11 = 2048, 11 2 have been used, and then a 2 can not make 2008

Given that the point P (x, y) is symmetric about the origin in the first quadrant, then the point Q (- y + 1, x-3) is symmetric about the X axis in the second quadrant______ quadrant
I'm the third quadrant. Y is positive and X is negative in the second quadrant. About X symmetry, isn't it the third quadrant? The answer is the first quadrant, and what's the meaning of the fourth quadrant

Because the symmetry point of P (x, y) about the origin is in the first quadrant, so p is in the third quadrant, X ＜ 0, y ＜ 0, so - y + 1 ＞ 0, x-3 ＜ 0. That is, q (- y + 1, x-3) is in the fourth quadrant. And the symmetry point of Q about the X axis is in the first quadrant