Mr. Zhang bought 4 copies of interesting mathematics and 4 copies of Story King, paid the salesperson 20 yuan, and recovered 7.6 yuan. Knowing that each interesting mathematics book costs 1.6 yuan, then each story king How much?

Mr. Zhang bought 4 copies of interesting mathematics and 4 copies of Story King, paid the salesperson 20 yuan, and recovered 7.6 yuan. Knowing that each interesting mathematics book costs 1.6 yuan, then each story king How much?

20-7.6=12.4
12.4-1.6x4=6.0
6.0/4=1.5
1.5 yuan per story

1. The equation of a line passing through a point a (1,2) on a circle x ^ + y ^ = 5 and tangent to the circle is?
2. If f (x) = x ^ + 1, G (x) = √ x, then f [g (2)] =?
3. If there are two intersections between the image of quadratic function y = x ^ - 4x + A-3 and X axis, then the value range of real number a is?
4. Given lgx lgY = a, then lg5x ^ 3 + LG 1 / 5Y ^ 3
5. Given cos (pai-a) = - 3 / 5, then sin (a-2pai) =?
6. If vector a = (3,4), vector B is opposite to a, and | B | = 15, then B =?
7. If a, B and C are in an equal ratio sequence, then the number of intersections between the image and the x-axis of the quadratic function y = ax ^ + 2bx + C is?
8. If 3sina + 2cosa / 2sina-7cosa = 1 / 11, Tana =?

1. The equation of a line passing through a circle X & # 178; + Y & # 178; = 5 and tangent to the circle is?
The derivation of X on both sides is 2x + 2yy ′ = 0, so y ′ = - X / Y; y ′ (a) = - 1 / 2, so the tangent equation through a is y = - (1 / 2) (x-1) + 2
=-(1/2)x+5/2.
2. If f (x) = x & # 178; + 1, G (x) = √ x, then f [g (2)] =?
F [g (x)] = x + 1, G (2) = √ 2, so f [g (2)] = f (√ 2) = √ 2 + 1
3. If the image of quadratic function y = x & # 178; - 4x + A-3 has two intersections with X axis, then the value range of real number a is?
Δ = 16-4 (A-3) = 28-4a > 0, so a

Finding the differential of (x ^ 2 + 2x + 3) ^ 3

The circumference of a rectangular vegetable field is 48 meters, and the ratio of length to width is 1 / 5:1 / 3. How many square meters is the area of this vegetable field?
Come on, don't solve equations

If the perimeter is 48 meters, the length + width = 48 △ 2 = 24 meters
The ratio of length to width is 1 / 5: 1 / 3 = 3:5
So length = 24 △ 3 + 5 × 3 = 9 meters
Width = 24-9 = 15m
So the area of this vegetable field is 9 × 15 = 135 square meters

The cubic product (- a) of (- a) square times (A's Square)

The original formula = A & # 178; × a to the sixth power × (- a)
=-The 9th power of a

A is not equal to 0, the solution of the equation AX + B = 0 is x = 1, try to find the solution of the equation ay-b = 0 about y?

x=1
That is, B = - A is substituted into the equation ay-b = 0
ay+a=0
∵ a ≠ 0, y + 1 = 0 can be obtained by dividing both sides of the equation by a at the same time
∴y=-1

A word used to describe the difficulty in walking or the difficulty in walking

Faltering

The volume of a cone is 15 cubic decimeters, the bottom area is 5 square decimeters, and its height is () decimeters?

The height is 15 × 3 △ 5 = 9 decimeters

Oral arithmetic in grade four of primary school
Oral problems, simple, in addition to oral problems, other do not, 30 questions a day, a total of 30 days, to 900 questions, the best no answer, there are also answers. Oral problems can be divided, multiplication, decimal addition and subtraction, division is best two digits divided by two digits (example: 91 △ 13 = 3), three digits divided by two digits, multiplication is best two digits by two digits or two digits by one digit, fast!

Finding the general solution of the differential equation XY '- 2Y = x3cosx

(by using the method of variation of constants) ∵ XY '- 2Y = 0 = = > dy / y = 2DX / x = = > ln ∵ y ∵ y = 2ln ∵ x ∵ + ln ∵ C ∵ (C is an integral constant) = = = > y = CX & # 178; ∵ let the solution of the original equation be y = C (x) x & # 178; (C (x) ∵ 178; (C (x) ? 178; (C (x) ? 178; (C (x