Practical problems of quadratic equations with two variables A supermarket sells 20 yuan for each teapot and 3 yuan for each teacup. The supermarket puts forward a promotion method: buy a teapot and get a teacup free. Xiaoming spends 170 yuan. Buy back the teapot and 38 teacups in total. How many teapots and cups do you buy back? A series of quadratic equations with two variables

Practical problems of quadratic equations with two variables A supermarket sells 20 yuan for each teapot and 3 yuan for each teacup. The supermarket puts forward a promotion method: buy a teapot and get a teacup free. Xiaoming spends 170 yuan. Buy back the teapot and 38 teacups in total. How many teapots and cups do you buy back? A series of quadratic equations with two variables

Xiaoming teapot, teacup each buy back x, y
x+y=38
20x+(y-x)*3=170
Solution
x=4
Then Xiaoming bought 4 teapots and 34 teacups

Add answers to the calculation questions of quadratic equations with 2 variables
If the calculation problem has a detailed process, such as 2x + 3Y = 16, x + 4Y = 13, what is the solution of the system of equations

Method 1,
2x+3y=16 ①
x+4y=13 ②
X = 13-4y (3) is obtained from (2)
Bring (3) into (1)
2（13-4y）+3y=16
26-8y+3y=16
5y=10
y=2
Say y = 3 and get x = 13-8 = 5
Method 2,
2x+3y=16 ①
x+4y=13 ②
② X 2 is 2x + 8y = 26 ③
③ (1) 5Y = 10
y=2
Let y = 2 be taken into 2
x+8=13
x=5
Hand only

x^2+5x^2y-24xy^2
Factorization

Solution
x²+5x²y-24xy²
=x(x+5xy-24y²)

In polar coordinates, the equation of a circle whose center is (2, π) and passes through the pole is______ ．

∵ in the polar coordinate system, the rectangular coordinate equation of the circle whose center is (2, π) and passes through the pole is: (x + 2) 2 + y2 = 2, that is, X2 + Y2 + 22x = 0. Its polar coordinate equation is: ρ = - 22cos θ. So the answer is: ρ = - 22cos θ

Known: as shown in the figure, in the triangle ABC, the angle ACB is equal to 90 degrees, the CD is high, and the angle a is equal to 30 degrees
Write the process down

If the angle a is equal to 30 degrees, then the angle B = 60 degrees, so the side opposite the angle DCB = 30 degrees in a right triangle is half of the hypotenuse. In the RT triangle ACB, the angle a = 30 degrees, so BC = 1 / 2Ab --- (1) in the RT triangle CDB, the angle DCB = 30 degrees, so BD = 1 / 2BC --- (2) (1) is substituted by (2), and BD = 1 / 2b is obtained

How many meters per second is 1km per hour

1000m / 60 * 60s = 1000 / 3600 = 0.28m/s

Known X0
Then 0

Brother, this is very easy to understand. What he means is that when loga B = 0, it means a = B,

The two diagonals of the diamond are ACM and BCM, and their perimeter and area are calculated

Area s = a × B / 2
Perimeter C = 2 √ (A & # 178; + B & # 178;) (all in brackets are under the following sign)

Related formulas of AC circuit with resistor inductor and capacitor in parallel

The impedance of capacitor: ZC = 1 / JWC, the impedance of inductor: ZL = 2 * (PI) * f * l, and the impedance of resistance (PI is the circumference) is R. if we want to find the impedance of parallel connection, we first change them into conductance, then add them and divide them by 1, the result is: 1 [R + 1 / 2 (PI) FL JWC]

It is known that a = {x | K + 1 ≤ x ≤ 2K}, B = {x | 1 ≤ x ≤ 3}, and a ⊆ B, then the value range of real number k is___ ．

① When K + 1 ＞ 2K, i.e. K ＜ 1, a = ∞, satisfies a ⊆ B, so K ＜ 1 is suitable for the topic. ② when K + 1 ≤ 2K, i.e. K ≥ 1, to make a ⊆ B, then K + 1 ≥ 12K ≤ 3, and K ≥ 1, the solution is 1 ≤ K ≤ 32