If x = 23 − 1, then the value of x2-2x + 3 is______ ．

If x = 23 − 1, then the value of x2-2x + 3 is______ ．

X = 23 − 1 = 3 + 1, ｜ x2-2x + 3 = (3 + 1) 2-2 (3 + 1) + 3 = 4 + 23-23-2 + 3 = 5

The square of (2x + 1) - 5 = 0
Quadratic solution equation of one variable

﹙2x+1﹚²-5=0
﹙2x+1﹚²=5
2X + 1 = √ 5 or 2x + 1 = - √ 5
X = 1 / 2 (√ 5-1) or x = - 1 / 2 (√ 5 + 1)

Mathematics problem three 7 and a 2 with addition, subtraction, multiplication, division and bracket arbitrary combination, finally equal to 51 how to do

7x(7+2/7)=51

Given sin (x + y) = 2 / 3, sin (X-Y) = 2 / 5, what is the value of TaNx / tany?

Sin(x+y)=sinxcosy+cosxsiny=2/3,
Sin (X-Y) = sinxcosy cosxsiny = 2 / 5
Sinxcosy = 8 / 15
Cosxsiny = 2 / 15
Then we can get sinxcosy / cosxsiny = TaNx / tany = 4

What kind of operation symbols and brackets should be added in the middle of the five 0.3 to make both sides of the equal sign equal 0.30.30.30.30.30.3 = 0

（0.3-0.3）*0.3*0.3*0.3=0

The function f (x) = tanwx (W > 0) has two adjacent tangent lines y = π / 8, and the length of the line segment is π / 8, then f (π / 8) =?

The period of F (x) is π / 8, that is, π / w = π / 8, so w = 8
So f (π / 8) = 0

1: Sublimation's father saved a sum of money in the bank for one year in 2008. The annual interest rate is 4.14%. After the maturity in 2009, the interest earned can just buy a bicycle with a price of 621. How much did sublimation's father save in 2008? (no interest tax)
2: In order to encourage residents to save water, a county mainly charges water charges to tap water users by section. If the monthly water consumption does not exceed 7 cubic meters, it is 1 yuan per cubic meter. If the monthly water consumption exceeds 7 cubic meters, the excess part is 2 yuan per cubic meter. If a resident pays 17 yuan, how many cubic meters does the household use in that month?
Column equation! Band analysis!

1. Sublimation's father saved 621 / (1 + 0.0414) = 596.31 yuan in 2008
2. The 17 yuan water fee includes: 7 cubic meters, 1 yuan per cubic meter, a total of 7 yuan, the remaining 17-7 = 10 yuan. The rest is 2 yuan per cubic meter, 10 / 2 = 5 per cubic meter. The monthly water consumption of this household is 7 + 5 = 12 cubic meters

Given that the point P (3, m) is a point on the parabola y ^ 2 = 4x, then the distance from P to the focus F of the parabola, the calculation process, thank you

For parabola y ^ 2 = 2px
The focal coordinate is (P / 2,0)
So the focus coordinate of the parabola y ^ 2 = 4x is (1,0)
Substituting P (3, m) into parabolic equation
m^2=12
So the distance from P to the parabolic focus f is
√[（3-1）^2+（m-0）^2]
=√16
=4
If you don't understand, please ask. If you understand, please select it as a satisfactory answer in time! (*^__ ^*)

The final sprint of grade 5 Volume 1 is 100 points. The reference answers of comprehensive knowledge accumulation and application of pass test secret volume
Urgent!
1、 Riddles.
1. No winter, no summer
2. Daughter getting married
3. Zero point
2、 The following are the founding emperors in Chinese history. Please write down the dynasties they founded.
Li Yuan Liu Xiu——
Nurhachi——
3、 What are the names of these ancient cities now?
Ying Tian Chang'an——
Dadu——
4、 What will gecko react to an attack? （　　　）
5、 Fill in plants, add poetry.
Most of all, one year's spring is better than smoke.
6、 Proverbs
1. The predecessors planted trees. 2. The banker is a flower.
3. Expert gatekeeper. It's good to be at home.
6._________ We will see people's heart after a long time.
7、 Xiehouyu
My nephew playing lantern——
A big girl in a sedan chair——
The blind cross the street——
Crane for chicken feather——

1、 1. Spring and autumn 2. Home 3. Midnight
2、 1. Tang Dynasty 2. Eastern Han Dynasty 3. Yuan Dynasty
3、 1. Nanjing 2. Xi'an 3. Beijing
4、 Break your tail and get out of danger
5、 Willow
6、 1. Descendants enjoy the cool; 2. All depend on dung; 3. Layman watch the door; 4. It's hard to walk out an inch; 6. You know horsepower by the distance
7、 1. As usual 2. Have a clear idea 3. Sooner or later 4. Don't know a good person 5. Be arrogant 6. Be sentimental 7. Be underutilized
You can choose me

The common chord of two circles x + y = 4 and X + y-6x = 0 is_____ ?
And what is a common string?

X + y-6x = 0 (x-3) + y = 9, so the center of the circle is a circle with (30) as the center and 3 as the radius. X + y = 4 and X + y-6x = 0 jointly solve the equation. There are two groups of line segment formulas at the intersection of two circles. Ah, the common string is the line connecting the intersection of two circles