The product of the difference between 8 and a certain number multiplied by 2 is 1. To find this number, we must use the equation solution Be quick

The product of the difference between 8 and a certain number multiplied by 2 is 1. To find this number, we must use the equation solution Be quick

Let this number be X
（8-x)×2=1
8-x=1/2
x=15/2=7.5
This number is 7.5

It is proved that if the root n is a rational number, then the root n is also a natural number

Proof: let n = P ^ 2 / Q ^ 2, P and Q be coprime integers, and then

9 * 6 equals 18 * 2. How many ratios can you write?

It should be 9 * 6 = 18 * 3
It can be written as:
18:9=6:3,9:18=3:6,6:3=18:9,3:6=9:18
18:6=9:3,6:18=3:9,9:3=18:6,3:9=6:18

Why is cos (π - 2 α) equal to - Cos2 α

cos(π-2α)=cosπcos2α+sinπsin2α
=-cos2α+0
=-cos2α

The equation of circle
1. Given that there is a point a (4, - 2) in the circle x2 + y2-4x + 6y-12 = 0, then the linear equation of the chord with a as the midpoint is -
2. The minimum and maximum distance between the moving point Q on circle x2 + y2-2x-2y + 1 = 0 and the straight line 3x + 4Y + 8 = 0 are -
3. When the line L passes through the point (- 5, - 10), and the chord length cut on the circle x2 + y2 = 25 is 5 √ 2, the equation of the line L is obtained
4. Given circle C: (x-a) 2 + (Y-2) 2 = 4 and line I: X-Y + 3 = 0, when the chord length of line I cut by circle C is 2 √ 3, find a
(there should be a process)

1. The standard equation of a circle is (X-2) & sup2; + (y + 3) & sup2; = 25, so the center O of the circle is (2, - 3), connecting the center of the circle and point a, the straight line OA is perpendicular to the chord, and the slope of OA K1 = [- 2 - (- 3)] / (4-2) = 1 / 2,
According to the vertical, K * K1 = - 1
The slope of the chord is k = - 2,
The linear equation is Y - (- 2) = - 2 (x-4)
It is reduced to 2x + y-6 = 0
2. According to the geometric relationship
The standard equation of a circle is (x-1) & sup2; + (Y-1) & sup2; = 1, so the o coordinate of the center of the circle is (1,1) and the radius is 1
The distance from the center O to the straight line L is d = L3 × 1 + 4 × 1 + 8L / √ (3 & sup2; + 4 & sup2;) = 3
According to the geometric meaning of the drawing, we can see that:
The minimum distance is d-radius 1 = 2
The maximum distance is d + radius 1 = 4
If the slope of the straight line L does not exist, because it passes through the point (- 5, - 10)
So the linear equation is x = - 5
At this point, the line is tangent to the circle and has no chord length, so the slope of the line exists
Let the slope of the line l be K, then the equation is Y - (- 10) = k [x - (- 5)]
That is kx-y + 5k-10 = 0
According to the equation of circle, the center of circle is (0,0) and the radius is 5
According to the geometric relationship, the distance from the center O to the straight line L is as follows:
D = under root sign [5 & sup2; - (5 √ 2 / 2)] = 5 √ 2 / 2
From the formula of distance from point to line, the distance from O to L is
d=5√2/2=l5k-10l/√（k²+1）
The solution is k = 1 or K = 7
So the linear equation is x-y-5 = 0 or 7x-y + 25 = 0
Because the chord length of line I cut by circle C is 2 √ 3, according to the geometric relationship
The distance from the center of the circle to the chord is d = under the root sign [2 & sup2; - (√ 3) & sup2;] = 1
According to the equation of circle C, we know the center of circle C: (a, 2) and radius r = 2
According to the distance between the center of the circle C and the line L: X-Y + 3 = 0 is 1, applying the distance formula from the point to the line, it is obtained that
d=1=la-2+3l/√2
The solution is a = - 1 + √ 2 or a = - 1 - √ 2

Put eight integers 1-8 in brackets to make the equation hold
The title is () = () () () 9 = () () () () () ()

(3) (1) = (2) (7) 9 = (5) (4) (1) (8)

How to solve the equation 60% X △ 15 = 30 x-80% x = 30 18-30% x = 6?

60%x÷15=30
0.6x=30*15
0.6x=450
x=450/0.6
x=750
x-80%x=30
0.2x=30
x=30/0.2
x=150
18-30%x=6
0.3x=18-6
0.3x=12
x=12/0.3
x=40

What is the equivalent of COS 53 and sin 53

Cos53 equals 0.6, sin53 equals 0.8

60% of a number is four fifths of 15. What's the number? 80% of a number is more than three fifths of 40. 5 find this number

1. Let this number be X
Then 60% x = 15x4 / 5
We get x = 20
2. Let this number be X
Then 80% x = 40x3 / 5 + 5
X = 36.25

A piece of cake, cut off 3 / 5 of it, Xiaojun ate 3 / 4 of it, Xiaojun ate how much of the whole cake?
For a piece of cake, cut off 1 / 3 of it for the first time, cut off the remaining 1 / 3 for the second time, cut off the remaining 1 / 3 for the third time, and how many parts are left?

A piece of cake, cut off 3 / 5 of it, Xiaojun ate 3 / 4 of it, Xiaojun ate how much of the whole cake?
A: Xiaojun ate 9 / 20 of the whole cake
For a piece of cake, cut off 1 / 3 of it for the first time, cut off the remaining 1 / 3 for the second time, cut off the remaining 1 / 3 for the third time, and how many parts are left?
A: in the end, one out of 27 is left