1 and 1 / 4 is 2 and 3 / 4 less than 2.5 times of a number. Find this number and use the solution of the equation

1 and 1 / 4 is 2 and 3 / 4 less than 2.5 times of a number. Find this number and use the solution of the equation

Let this number be X
2.5x-1 and 1 / 4 = 2 and 3 / 4
2.5x = 2 and 3 / 4 + 1 and 1 / 4
2.5x=4
x=1.6

Given that x = 5 is the solution of the equation AX-8 = 20 + A, find a
Don't copy! I can see it!

5a-8=20+a
4a=28
a=7

(5 / 6 + 5 / 8) × x = 7 / 20 (equation plus process)

5x of 6 + 5x of 8 = 7 of 20
35x of 24 = 7 of 20
X = 6 / 25

As shown in the figure, if the positive scale function y = 3x and the inverse scale function y = KX (K ≠ 0) intersect at point a in the first quadrant, and AO = 2, then k = 0___ ．

Let the coordinates of point a be (x, 3x).. Ao = x2 + (3x) 2 = 2, ‖ x = 1 or x = - 1 (negative value is not in the meaning of the question, which means that the coordinates of point a are (1, 3).. k = 1 × 3 = 3

Rearrange the following letters into words
1.olcclet
2.tapsm

1.collect
2.stamp

Expand the side of a cylinder to get a square with side length of 12.56 decimeters. Find the surface area and volume of the cylinder?

12.56/3.14/2 = 2 (CM) - radius
3.14 * 2 ^ 2 = 12.56 (cm ^ 2) -- bottom area
12.56 * 12.56 = 157.7536 (cm ^ 3) -- volume
12.56 * 12.56 + 12.56 * 2 = 182.8736 (cm ^ 2) -- surface area

Add appropriate operation symbols and brackets to the left side of the equal sign below to make the calculation result exactly equal to the right side
3○3○3○3=4

（3×3+3）÷3=4

Let f (x + y, XY) = x & # 178; + Y & # 178; + XY, then DF (x, y)=

f(x+y,xy)=x²+y²+xy
=x²+y²+2xy-xy
=(x+y)²-xy
f(x,y)=x²-y
df(x,y)/dx=2x
df(x,y)=2xdx
df(x,y)/dy=-1
df(x,y)=-dy
therefore
df(x,y)==2xdx-dy

If the function f (x) satisfies that f (x + 1 / 2) = the square of X + 1 / 2 of X, then f (x) =?

f(x+1/x)=x^2+1/x^2=(x+1/x)^2-2﹙x≠0﹚
Let x = x + 1 / x, X ∈ (- ∞, - 1] ∪ [1, + ∞)
Then f (x) = x ^ 2-2

ABCD multiplied by 9 equals DCBA, and ABCD is not the same number. How many four digit books is ABCD?

ABCD × 9 = DCBA because DCBA is still four digits, so a must be 1, otherwise ABCD × 9 will not be four digits, and because the single digit of D × 9 is 1, so d must be 9. Write the formula as 1 bc9 × 9 = 9CB 1, because B × 9 has no carry (otherwise a × 9 + carry product is not four digits), so B must be 0 (because a = 1) and