For a circle 4 cm in diameter, find the perimeter and area

For a circle 4 cm in diameter, find the perimeter and area

4x3.14＝12.56
4÷2＝2
2x2x3.14
＝4x3.14
＝12.56

How to calculate the circumference and area of a circle, including how to find the radius and diameter when I know the radius and diameter. And how to find the radius and diameter when I know the circumference and area. It can be expressed in letters. The exam is about to take place

Let R be the radius and d be the diameter
Then perimeter C = 2 π r = π D, then r = C / 2 π d = C / π
Area s = π R & # 178; = π (D / 2) &# 178; then r = √ (s / π) d = 2 √ s / π

Xiao Li subtracts a 36 square centimeter square from each corner of a square piece of paper, and then folds it to make a cuboid box without a cover. The volume of the box is 150 cubic centimeter, and the side length of the original square is calculated

The side length of the cut square is 36 △ 6 = 6 (CM)
The height of the box is six centimeters
The bottom area of the box is 150 △ 6 = 25 (square centimeter)
Side length of box bottom × side length = 25
Bottom side length of box = 5 (CM)
The length of the original square is 5 + 6 × 2 = 17 (CM)
A: the length of the original square is 17 cm

Xiao Li and Xiao Jie are scheduled to go to the nursing home for cleaning. Xiao Li goes every six days and Xiao Jie goes every eight days. If they both clean in the nursing home on March 1, where will they meet next

Our teacher said it was on May 3. It must be true
（6+1）*（8+1）=63
March 1 + 63 days = May 3
believe me
Upstairs, 6 + 1 = 8. Dizzy. How to learn math

Xiaoqiang got 95 points in the exam, 5 points more than Xiaoli's 8:9. How many points did Xiaoli get?

95-5 = 90 (points)
90 △ 9 / 8 = 80 (min)

It is known that: x + y = 1 to find 1 / 4x & # 178; + MXY + 25y & # 178; is a complete square formula to find the value of M
sorry. Wrong title, the real Title: known x + y = 1, find the value of 1 / 2x & # 178; + XY + 1 / 2Y & # 178;, thank you!!

Original formula = 1 / 2 (X & # 178; + 2XY + Y & # 178;)
=1/2(x+y)²
=1/2×1²
=1/2
In addition, if the square is complete, then M = ± 5

It is known that the value of B can be obtained by completely flat 1 / 4x & # + BX + 9

Let X & # 178; / 4 + BX + 9 = 0, △ = B & # 178; - 4 * 1 / 4 * 9 = 0
So B & # 178; - 9 = 0, the solution is b = 3 or - 3

Given the polynomial X & # 178; + 1, now add a term to make it a complete square. How many methods can you have,

+2x .(x+1)²
-2x.(x-1)²
+1/4x².(x+1/2x)²
+x^4/4 .(x²/2+1)²
-1.x ²

It is proved that a (a + 1) (a + 2) (a + 3) + 1 is a complete square form

∵ a (a + 1) (a + 2) (a + 3) + 1 = (A2 + 3a) [(A2 + 3a) + 2] + 1 = (A2 + 3a) 2 + 2 (A2 + 3a) + 1 = (A2 + 3A + 1) 2, ∵ a (a + 1) (a + 2) (a + 3) + 1 is a complete square

It is proved that a (a + 1) (a + 2) (a + 3) + 1 is a complete square form

∵ a (a + 1) (a + 2) (a + 3) + 1 = (A2 + 3a) [(A2 + 3a) + 2] + 1 = (A2 + 3a) 2 + 2 (A2 + 3a) + 1 = (A2 + 3A + 1) 2, ∵ a (a + 1) (a + 2) (a + 3) + 1 is a complete square