There are 1200 popular science books in the school library. Among them, popular science books are 5 / 1 more than story books. How many story books are there in the library?

There are 1200 popular science books in the school library. Among them, popular science books are 5 / 1 more than story books. How many story books are there in the library?

Er, it's a little unclear whether your popular science books are 5 / 1 more than story books, and whether they are one fifth or one fifth, but let's do it for you!
One fifth: 1200 (1 + 1 / 5) = 1000 (this)
5 / 1: 1200 ÷ (1 + 5) = 200

In the school library, story books account for 1 / 3 of the total and popular science books account for 2 / 5 of the total
I will. Thank you all

The topic is a bit confusing

There are 640 popular science books in the school library, accounting for 2 / 7 of all books and 1 / 4 of all books. How many story books are there in the school

640 / (2 / 7) times 1 / 4 = 560

The school library has 120 popular science books, accounting for 25% of the total number of books. Story books account for 5 / 3 of the total number of books. How many story books do the school library have

120 △ 25% = 480 (this) Total number of books
480 * 3 / 5 = 288 storybook

Given (A-1) ^ 2 + | B + 3 | = 0, find the value of 2 (- A ^ 2 + 3ab-1 / 2B ^ 2) - 4 (- 2A ^ 2 + 4ab-b ^ 2)

The area of a triangular wheat field is 0.18 hectares, the bottom is 90 meters, how many meters high?

18 ha = 1800 m2, bottom is 90 m, height is 1800 × 2 △ 90 = 40 m

Let a > b > 1, and loga (b) + log (b) a = 10 / 3, find loga (b) - log (b) a

It is known that log (a) B + 1 / (log (a) b) = 10 / 3
Let x = log (a) B; because a > b > 1, so log (a) B

If the square + X + m of polynomial x can be divided by X + 5, then the word polynomial can also be divided by the following Polynomials: a.x-6 b.x + 6 c.x-4. D.X + 4
Please explain why

m=-20
x^2+x-20=(x+5)(x-4)
C.x-4
process
Let x + n
x^2+x+m=（x+n）（x+5）=x^2+（5+n）x+5n
5+n=1
n=-4

Let △ ABC be an equilateral triangle, ab = 2, P and Q be the points on AB and AC respectively, and the segment PQ divide △ ABC into two parts with equal area, let AP = x, AQ = Z and PQ = y
1. Express y as a function of X, and find the value and domain of the function
2. Express Z as a function of X, and find the value and domain of the function

Because the area ratio of Apq and ABC is 1 / 2, so AP * PQ / (AB * BC) = 1 / 2
That is, XZ = 2 * 2 / 2 = 2.01
According to the cosine theorem, we know that y ^ 2 = x ^ 2 + Z ^ 2-xz = x ^ 2 + Z ^ 2-2. Y = root (x ^ 2 + Z ^ 2-2)
Y = root (x ^ 2 + 4 / x ^ 2-2). The definition field is (1,2). The value field is [root 2, root 3]
2. Z = 2 / X. range (1,2), domain (1,2)

Given the parabola y = - x ^ 2 + 2, passing through a point P above it, the tangent l of the parabola is introduced to minimize the area of the triangle bounded by L and two coordinates in the first direction, and the tangent of the tangent L is obtained

Let the tangent point p be (a, - A ^ 2 + 2), and the derivative of y = - x ^ 2 + 2 has y = - 2x, so the slope of tangent is k = - 2A, so let the tangent be y = - 2aX + 2 + A ^ 2. Since the triangle is in the first quadrant, the intercept of x-axis and y-axis is (a ^ 2 + 2) / 2a, 2 + A ^ 2 respectively, then the area of triangle is 1 / 2 * (a ^ 2 + 2)