Under the teacher's education, I corrected my learning purpose and attitude

Under the teacher's education, I corrected my learning purpose and attitude

In the teacher's education, I correct the attitude of learning. Purpose can not be correct

A two digit number, the sum of the digits is 8, and the two digits obtained by the transposition of the single digit and the ten digit number are 18 less than the original two digits
Then the original number is

Let X be the one digit, then 8-x is the ten digit
So it's 10 (8-x) + X
The swap is 10x + (8-x)
So 10 (8-x) + x = 10x + (8-x) + 18
80-9x=9x+26
18x=54
x=3
8-x=5
A: the original number is 53

The solution set of inequality 3-4x ≤ 11-2x is fast

3-4x≤11-2x
3-11-4x+2x≤0
-8-2x≤0
2x+8≥0
2x≥-8
x≥-4

The radius of the ball is r cm, the volume is 500 π cubic cm, find the value of R (accurate to 0.01 cm)
&2. The volume of a cylinder is 26 π M & # 179;, the diameter of the bottom circle is equal to the height of the circle, and the bottom radius of the circle is calculated to 0.01
3. For a right triangle, the right side is √ 3cm, and the hypotenuse is √ 30cm. Calculate the area of the triangle

1、
V=(4/3)πr^3
r3=500π/（4/3）/π=375cm
r≈7.21
2、
V=πr2h
h=2r
V=2πr3=26π
r3=13
r≈2.35
3、
√30-3=√27
S=√3×√27/2=√81/2=9/2=4.5cm2

Proving the coordinates of the center of gravity of a triangle with vectors
Let the coordinates of vertex a, B and C of triangle ABC be (x1, Y1), (X2, Y2), (X3, Y3) respectively
It is proved that the coordinates (x, y) of the center of gravity (i.e. the intersection of the three midlines) m of triangle ABC satisfy the following conditions:
X=X1+X2+X3/3 Y=Y1+Y2+Y3/3

Let the midpoint of AB be d
∴Dx=(x1+x2)/2,
And M is the center of gravity of the triangle, CD = 3MD,
∴x3-(x1+x2)/2=3[x-(x1+x2)/2]===>x=(x1+x2+x3)/3
Similarly: y = (Y1 + Y2 + Y3) / 3

For real numbers x and y, what is the condition to judge that "x + y is not equal to 8" is "x is not equal to 2 or Y is not equal to 6"

Let a be: x + y is not equal to 8, and B be: X is not equal to 2 or Y is not equal to 6, then a can not deduce B (counterproof: hypothesis is true, when x = 2, y = 7, the result is not consistent, the hypothesis is not tenable.) B can not deduce a (counterproof: hypothesis is true, when x = 1, y = 7, the result is not consistent, the hypothesis is not tenable.)

Higher number DF (x) = f (x) DX
Is that it? How to understand it

The variable of function f (x) is a function f (x) with X as the variable

Let α 1, α 2 α n is a set of n-dimensional vectors. The n-dimensional unit coordinate vectors E1, E2 It is proved that α 1, α 2 α n is linearly independent

It is proved that any group of n-dimensional vectors can be expressed linearly by the group of n-dimensional unit vectors, that is, α 1, α 2 α n can be represented by n-dimensional unit coordinate vectors E1, E2 The n-dimensional unit coordinate vectors E1, E2 The results show that, en can be determined by α 1, α 2 α n is a linear representation of "∩ α 1, α 2 ，...

The general steps of implicit function differentiation

The independent variable and the dependent variable are differential to the parameter variable respectively

Finding the derivative of y = root (4-x ^ 2)

y=√(4-x²)
Let t = 4-x & sup2;, t · = - 2x, y = √ t
∴y·=1/(2√t)*t·
=-x/√(4-x²)