If the square of X - 7x + 1 = 0, then the square of X + 1 / X=

If the square of X - 7x + 1 = 0, then the square of X + 1 / X=

transposition
x²+1=7x
Divide both sides by X
x+1/x=7
Square on both sides
x²+2+1/x²=49
x²+1/x²=47

There are two classes in Grade 6 of a school. Now they are divided into three classes. One third of the original class 1 and one fourth of the original class 2 form a new class 1. One fourth of the original class 1 and one third of the original class 2 form a new class 2. The remaining 60 people form a new class 3. If the number of the new class 1 is 1 / 10 more than that of class 2, what is the number of the new class 1?
For a formula, only one unknown number can be set

The number of new class 3 is 5 / 12 of the original two classes, so 60 / 5 / 12 = 144 (people) 144-60 = 84 (people)
84 (1 + 1 + 1 / 10) = 40 (people) 84-40 = 44 (people) the number of new class 1 is 44

If one side of a square increases by 2cm and the other side decreases by 3cm, the area of the rectangle will be reduced by 14cm
The length of the side of a square

Let the side length of a square be x, then if one side increases by 2cm, the area will increase by 2x. At this time, if the other side decreases by 3cm, then the area of the new rectangle will decrease by 3 (x + 2). Therefore, the difference between the increase and decrease of the area is 14. That is: 3 (x + 2) - 2x = 14. The solution is x = 8cm, that is, the side length of the square is 8cm

The orbit of a planet and the earth around the sun can be regarded as a circle. Every n years, the planet will move to the extension line of the sun earth line, as shown in the figure. The ratio of the radius of revolution of the planet and the earth is___ ．

A. B, C, D: it can be seen from the figure that the orbit radius of the planet is large, so the period is long according to the third law of Kepler. Every n years, the planet will run to the extension line of the sun earth line, which means that from the initial extension line of the sun earth line, the earth will turn one nth of the circle in front of the planet every year

The main reason is that ()
A. The recording effect of tape recorder is poor, and the sound is distorted after recording. B. listening to your own voice and listening to the voice of tape recorder are caused by different ways of sound transmission. C. the tape recorder changes the sound signal into electromagnetic signal and then into acoustic signal, and the tone of the sound changes. D. the tape recorder changes the sound signal into electromagnetic signal and then into acoustic signal, and the timbre of the sound changes

When you hear your voice recorded by a tape recorder, it is transmitted by gas. When you listen to your voice, it is mainly transmitted through bone. The effect of bone conduction is better than that of air conduction. So it doesn't sound like your own voice. So choose B

The circumference of a rectangle is 120 cm. If the length is reduced by 10 cm and the width is increased by 6 cm, the rectangle will become a square. What is the area of the original rectangle?

Length + width = 120 ÷ 2 = 60cm, let the width of rectangle be x, then the length is 60-xcm, the later length is 60-x-10cm, the later width is x + 6cm, 60-x-10 = x + 6, & nbsp; 50-x = x + 6, & nbsp; & nbsp; & nbsp; & nbsp; 2x = 50-6, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2x = 44, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 22, length: 60-22 = 38 (CM), area: 38 × 22 = 836 (square cm). A: the area of the original rectangle is 836 square cm

Simple calculation: (1) 27 / 9 2 × 81 / 7 (2) 12 / 5 × 3 / 4 + 12 / 31 / 4 / 3 (3) 7 / 5 × 14 / 9 / 15
(4) (34 / 5 + 17 / 19) △ 17 / 19

(1) 27 / 9 2 × 81 / 7 = 27 / 2 9 × 81 / 7 = (27 / 81 / 7) × 2 / 9 = 3 / 7 × 2 / 9 = 2 / 21 (2) 12 / 5 × 3 / 4 + 12 / 31 / 4 = 12 / 5 × 3 / 4 + 12 / 31 × 3 / 4 = (12 / 5 + 12 / 31) × 3 / 4 = 3 × 3 / 4

Given the function f (x) = - 2x ^ 2 + 4x, the domain of definition is [0, M], and the range of value is [0,2]. Find the value range of real number M

f(x)=-2x^2+4x=-2(x-1)^2+2
From the function f (x), we can see that its maximum value is 2, where x = 1;
When f (x) = 0, X is 0 or 2
According to the meaning of the title, f (x) is defined as [0, M], and the value range is [0,2],
So 1 ≤ m ≤ 2

A rectangle is 3cm long and 2cm wide
A rectangle has a length of 3cm and a width of 2cm. It rotates around its length and width to form two different cylinders. How big is the volume of that cylinder?

The volume of the cylinder is 3.14 × 2 × 2 × 3 = 37.68 cubic centimeter
The volume of the cylinder is 3.14 × 3 × 3 × 2 = 56.52 cubic centimeter
Therefore, the volume of the cylinder rotated on the width axis is larger: 56.52-37.68 = 18.84 cubic centimeter

3,4, - 6,10 use the above rules to write three different formulas, so that the result is equal to 24
Write down three different forms. Give me a reply in two minutes

3*(10-4)-(-6)
3*(10+4-6)
4-[(-6)/3*10]