There are 488 science and technology books in the school library, 126 less than twice as many as literature and art books. How many literature and art books are there,

There are 488 science and technology books in the school library, 126 less than twice as many as literature and art books. How many literature and art books are there,

Suppose there are two books of literature and Art: 2 × - 126 = 488 2 × = 126 + 488 2 × = 614 × = 307

There are three men and two women. Two people are randomly selected to participate in the activity, and the probability of one man and one woman is?

3*2/C(5,2)=6/10=3/5

How to find the range of quadratic function

For example: y = ax ^ 2 + BX + C = a [x ^ 2 + BX / A + (b ^ 2) / (4a ^ 2) - (b ^ 2) / (4a ^ 2)] + C = a (x + B / 2a) ^ 2-A (b ^ 2) / (4a ^ 2) + C if - B / 2a is in the domain, because a (x + B / 2a) ^ 2 is greater than 0, so when x is any real

How to solve the equation of 5 * 11x-10) / (11x) = (5 * 7x + 10) / (7x + 4), step by step!

Extracting the common factor, we get [5 (11x - 2)] / (11x) = [5 (7x + 2)] / (7x + 4)
Divide both sides by 5 to get (11x - 2) / (11x) = (7x + 2) / (7x + 4)
Remove the denominator and get (11x - 2) (7x + 4) = (7x + 2) (11x)
Remove the brackets and get 77X & # 178; + 44x - 14x - 8 = 77X & # 178; + 22x
If we simplify, we get x = 1

2 (A2 + B2) (a + b) 2 - (A2-B2) 2 factorization,

(a \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\b) & # 178;] = (a + b)

In △ ABC, the bisector of ∠ C intersects AB at D, and the bisector of BC intersects AC at e through D. given BC = a, AC = B, the length of De can be obtained

∵ de ∥ BC, ∥ 1 = ∥ 3. And ∥ 1 = ∥ 2, ∥ 2 = ∥ 3DE = EC, from △ ade ∥ ABC, ∥ DEBC = aeac, DEA = B − DEB, B ∥ de = AB-A · De, so de = ABA + B

How many meters were one inch, one foot and one foot in the past?
Such as the title

One meter is three feet
One foot is ten feet, one foot is ten inches

The length of a school teaching building is 60 meters. On the campus plan with a scale of 1:600, how many centimeters should the teaching building be drawn?
It's just a formula, not a calculation!

60m = 6000cm
6000 / 600 = 10 cm

It is proved that the sum of squares of the three middle lines of a triangle is equal to 3:4
Such as the title

Let △ ABC, ab = C, AC = B, BC = a; the middle line am = ma & nbsp; & nbsp; (a is the subscript) on the side of BC, and the middle line MB on the side of AC and MC on the side of ab
Extend am to a & # 39;, make Ma & # 39; = am, connect a & # 39; B and a & # 39; C, and divide AA & # 39; and BC equally, so that ABA & # 39; C is a parallelogram (as shown in the figure)
Its opposite sides are equal and its adjacent angles complement each other. In the graph, ∠ BAC is an acute angle and ∠ ACA & # 39; is an obtuse angle;
In △ ABC, B & # 178; + C & # 178; - 2bccosbac = A & # 178;, that is & nbsp; B & # 178; + C & # 178; - A & # 178; = 2bccosbac; & nbsp; ① & nbsp;
In △ AA & # C, AC + A & # 39; c-2ac * A & # 39; ccosaca & # 39; = AA & # 39; &# 178;, where cosaca & # 39; = - cosbac, AA & # 39; = 2mA,
∴4ma²-（b²+c²）=2bccosBAC； ②
Combining ① and ②, we get 4mA & # 178; - (B & # 178; + C & # 178;) = B & # 178; + C & # 178; - A & # 178;, that is, 4mA & # 178; = 2B & # 178; + 2C & # 178; - A & # 178;;
Similarly, for other midlines, there are & nbsp; 4MB & # 178; = 2A & # 178; + 2C & # 178; - B & # 178;, & nbsp; & nbsp; & nbsp; 4mc & # 178; = 2B & # 178; + 2A & # 178; - C & # 178;, & nbsp; & nbsp;,
The left and right ends of the three formulas are respectively added and sorted into 4 (MA & # 178; + MB & # 178; + MC & # 178;) = 3 (A & # 178; + B & # 178; + C & # 178;)
∴（ma²+mb²+mc²）/（a²+b²+c²）=3/4.

How to solve the square of x-2x + 1-A ＞ 0

B-4ac = 4-4 (1-A) = 4A, 4A ≥ 0, when 4A = 0, x = 1, when 4A > 0, x = 1 + A, x = 1-A