The number of pencils in the stationery shop is twice that of pens. Every day, 15 pens and 20 pencils are sold out. After a few days, there are still 80 pencils left. How many pens and pencils are there in the stationery shop?

If x pens are used, there will be 2x pencils
(2x-80):x=20:15
Solution
x=120
So the original pen 120, pencil 240

Use 48 pens, 72 pencils and 36 ballpoint pens to make some stationery gift boxes. The number of three pens in each gift box is the same. There are at least several pens in a gift box

【48.72.36】=12 48/12=4 72/12=6 36/12=3
3 + 4 + 6 = 13

Stationery stores sell 30 pencils more than pens, and 30% less than pencils. How many pens do they buy?

Let's sell x pencils and (X-30) pens
30/x=30%
x=100
x-30=70
A: I bought 70 pens

Calculate {A-B + 2C} {B + a-2c}

=[a+(2c-b)][a-(2c-b)]
=a^2-(2c-b)^2
=a^2-(4c^2+b^2-4cb)
=a^2-4c^2-b^2+4cb

In the plane rectangular coordinate system xoy, the parabola C: y2 = 2px (P > 0) is known. The distance between a point m (2, m) and the focus is 3,
In the plane rectangular coordinate system xoy, it is known that the parabola C: y2 = 2px (P > 0). The distance from a point m (2, m) on the parabola to the focus is 3,
(1) Find the equation of this parabola
(2) The Quasilinear of parabola C intersects with X axis at point m, and the straight line L passing through point m with slope k intersects with parabola C at points a and B. whether there is such a K, so that there is always a point Q (x0, Y0) on parabola C satisfying QA ⊥ QB, if there is, the value range of K is obtained; if not, the reason is given

Question 1: the distance from m to the focus is equal to the distance to the collimator, so p / 2 + 2 = 3, so p = 2, so the equation is y square = 4x

How to convert the liter and kilogram of Nippon Paint for exterior wall

If the specific gravity of the product is 1.4, it will weigh 1.4 kg per liter
Nippon coatings has many products, the proportion is not the same. Look at the product manual to know

Factor of 56... 75

1.2.4..7.8.14.28.56

The mathematical function FX = x2 + 1, and GX = f [f (x)], G (x) = g (x) - a f (x),
Given the function FX = x2 + 1, and GX = f [f (x)], G (x) = g (x) - a f (x), is there a real number a such that G (x) is a decreasing function on (negative infinity, - 1] and an increasing function on (- 1,0)
Suppose there is a real number a, such that G (x) is a decreasing function on (- 1,0) and an increasing function on (- 1,0)
f(x)=x²+1
g(x)=f[f(x)]=[f(x)]²+1=(x²+1)²+1=x^4+2x²+2
G(x)=g(x)-af(x)= x^4+2x²+2-a(x²+1)=x^4+(2-a)x²+2-a
The function g (x) can be regarded as a combination of the function u = T & # 178; + (2-A) t + (2-A) and the function T = x & # 178,
It is easy to know that the function T = x & # 178 is a decreasing function on (- ∞, 0),
Let g (x) be a decreasing function on (- 1,0) and an increasing function on (- 1,0)
Then the function u = T & # 178; + (2-A) t + (2-A) is a decreasing function in (0,1) and an increasing function in (1, + ∞)
∴-(2-a)/2=1,
2-a= -2,
a=4,
Therefore, there exists a = 4 such that G (x) is a decreasing function on (- 1,0) and an increasing function on (- 1,0)
How do you understand the sentence in the last four lines above?

How do you understand the sentence in the last four lines above?
The image of the quadratic function u = T & # 178; + (2-A) t + (2-A) with respect to t is a parabola with an opening upward,
Its axis of symmetry is: x = - (2-A) / 2
The function u = T & # 178; + (2-A) t + (2-A) is a decreasing function in (0,1) and an increasing function in (1, + ∞)
X = - (2-A) / 2 = 1

What are the storage conditions of liquid oxygen? Under what conditions can it be converted into gaseous oxygen?
Liquid oxygen weight (g) × 22.4 = gaseous oxygen (L)

The storage condition of liquid oxygen is: low temperature and high pressure compression, decompression and heating can be converted into gaseous oxygen
Please express the formula well before you ask

Given x ^ a = 3, x ^ B = 5, then the value of x ^ (3a + 2b) is

X ^ (3a + 2b)
x^3a+x^2b=x^a×x^a×x^a+x^b×x^b×x^b=3×3×3+5×5×5=27+125=152

The number of pencils in the stationery shop is twice that of pens. Every day, 15 pens and 20 pencils are sold out. After a few days, there are still 80 pencils left. How many pens and pencils are there in the stationery shop?