The school library has 290 literature and art books, 40 more than twice the number of science and technology books. How many science and technology books does the school library have? (solved by equation)

Suppose the library has x science and technology books, 2x + 40 = 290 & nbsp; & nbsp; 2x = 250 & nbsp; & nbsp; & nbsp; X = 125 A: the library has 125 science and technology books

There are 180 literature and art books in the school library, 20 more than twice the number of science and technology books. How many are there in total?

250 copies

There are 2400 science and technology books and literature and art books in the library. It is known that the ratio of science and technology books to Literature and art books is 5:3

5+3=8,2400/8=300
Science and technology book 300 * 5 = 1500
Literature and Art Book 300 * 3 = 900

43a8b can be divided by 5 and 9 to find a and B at the same time

If B = 0, then 43a80 must be divisible by 9, and the number divisible by 9 also has a characteristic, that is, the sum of all digits is a multiple of 9, so 4 + 3 + A + 8 + 0 = 15 + A is a multiple of 9, and a can only be a number from 0 to 9, then a = 3

If P is the moving point on the ellipse x ^ 2 / 25 + y ^ 2 / 9 = 1, and F1 and F2 are the two focal points of the ellipse, then | Pf1 | PF2 | is the minimum

A & sup2; = 25A = 5, so Pf1 + PF2 = 2A = 10pf1 & sup2; + PF2 & sup2; + 2pf1 * PF2 = 100pf1 & sup2; + PF2 & sup2; = 100-2pf1 * pf2b & sup2; = 9, C & sup2; = A & sup2; - B & sup2; = 16b = 4f1f2 = 2C = 8, pf1-pf2 in triangle pf1f2|

What are the prime numbers that can make up 40?
You can plagiarize, but you can't answer "I don't know", "..." "What kind of teacher am I, kid? You need to type out the questions “……

40=2+19+19
40=2+7+31

Let f (x) = loga (3-ax) be a decreasing function on [0,1]; (1) find the range of real number a; (2) find the monotone increasing interval and range of G (x) = a ^ (- x ^ 2 + 2x)

1. Basic knowledge: 00;
2. When x increases, 3-ax decreases, and because the whole function decreases, it can only be a > 1;
3. When x = 1; 3-ax is the minimum, that is 3-a. 3-A > 0, a is required

If the image of the function y = loga (x + 3) - 1 (a > 0, a ≠ 1) passes through the fixed point a, if the point a is on the straight line MX + NY + 1 = 0, where m, n > 0, then the minimum value of 1m + 2n is ()
A. 6B. 8C. 4D. 10

The image of the function y = loga (x + 3) - 1 (a > 0, a ≠ 1) passes through the fixed point a (- 2, - 1). Substituting the point a into the straight line MX + NY + 1 = 0, we can get - 2m-n + 1 = 0, which is reduced to 2m + n = 1. ∵ m, n > 0, ∵ 1m + 2n = (2m + n) (1m + 2n) = 4 + nm + 4Mn ≥ 4 + 2nm · 4Mn = 8. If and only if n = 2m = 12, we take the equal sign. ∵ 1m +

Given x + 2Y = 1, y + 2Z = 2, 2x + 3Z = 3, what is the value of X + y + Z
Given x + 2Y = 1, y + 2Z = 2, 2x + 3Z = 3, then the value of X + y + Z is []
A .0 B .1 C .2 D .3

The sum of the three equations leads to
3x+3y+3z=1+2+3
3x+3y+3z=6
∴x+y+z=2
Choose C
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Let the joint probability density of two-dimensional random variables (x, y) be the - (3x + 4Y) power of F (x, y) = Ke

Use the probability density integral to calculate the first-class property. The economic mathematics team will help you to solve it, please adopt it in time

The school library has 290 literature and art books, 40 more than twice the number of science and technology books. How many science and technology books does the school library have? (solved by equation)