Math problems, first aid SOS, help, I m going to zzz

Method 1: Set up a math book x book and a picture book y book.

The solution is x=18

y=10 so there are 18 math books and 10 picture books.

Method 2: If you set the math book x book, then the picture book has (

The solution is x=18

y=(So 18 math books and 10 picture books.)

Let the number of exercise books be x and the number of picture books be y

o⊙)…The landlord will solve it himself.。。。

If you want to buy a copy of the exercise book, a copy of the drawing book, and a system of equations from the question:

solution, we get a= 18, b=10

Let the math book be x and the picture book be y

So the solution is x=

Set up x books of drawings and practice y books.

Next, you can solve it yourself, alas, I hit it with my mobile phone, I am tired to death! The landlord gives a few points.

As shown in the figure, (1) from the meaning of the title, we can know that be=bp 2, ce=2cf, af=2aq, and because it is an equilateral triangle, a= b= c=60°. Rule.

y=[2-(2-x 2) 2] 2=(4+x) 8, and 0 x<2

2) The point p coincides with the point q, that is, y+x=2, combined with y=(4+x) 8, and the solution is x=4 3

So when the length of bp is equal to 4 3, the point p coincides with the point q.

3) When BP is greater than 4 3, that is, X>4 3, the line segment PE and FQ intersect, and the circumference of the triangle enclosed by the line segment PE, EF and FQ is the longest.

In addition, because the triangle enclosed by the line segments PE, EF and FQ is also an equilateral triangle (it can be inferred from the three perpendicular lines and the equilateral triangle ABC), when P and A coincide, the circumference of the triangle enclosed by the line segment PE, EF and FQ is the shortest.

PE=X 3 2, EF=(4-X) 3 4, FQ=(4+X) 3 8, so the circumference of the triangle enclosed by PE, EF and FQ is c=3*(4-x) 3 4,3*(4-2) 3 4 C<3*(4-4 3) 3 4, so the range of the perimeter of the triangle enclosed by PE, EF and FQ is [3 3 2 , 2 3).

(1) Because bp=x, so be=x 2, so ce=2-x 2, so cf=1 2(2-x 2), so af=2-1 2(2-x 2), so aq=1 2af=1 2<2-1 2(2-x 2)>=1 2+x 8

2) Because the point p coincides with the point q, so ap+bq=2 is x+y=2, so: 1 2+x 8+x=2 so x=4 3 is bp=4 3

Solution: (1) y= (you can first take two special values, such as x=2 x=1, and find y= y= and then set y=kx+b to solve the equation according to the hypotenuse length of a right-angled triangle of 30° = 2 and the length of the short right-angled side of 30°).

2) When the bp length is 4 3, pq coincides (i.e., y+x=2 y= solves the system of equations).

3) Root number 3-4 3 (equilateral triangle minus the area of four right-angled triangles [PE and FQ intersect, i.e. pq coincide, and four congruence can be calculated]).

A and B were both or Changbi C and had 6 more rents.

6*2 3=4, you should take 4 per person.

This means that both A and B take 2 eggplant trillions from C. Worth a lot of money.

Dollar per cake.

Both A and B have 6 more holes than C;

There are 12 more cakes, and each person should be divided into 4; Now A and B each get six;

Therefore, A and B have nothing but their own share; also "deprived" each person of 2 pre-C banquets;

as compensation; Each of them was given a penitent;

i.e. two cake yuan;

Dollar per cake.

The title was copied incorrectly... I guess the a vector is (-1,1).

Find the two vectors as (a,1) and (4,a) respectively, and then compare the value of a square equal to 4, and solve a is equal to 2 or -2, because the same direction is parallel and parallel, so a = 2

Solution: "Translated" into "pure mathematics" language to understand, the "knowledge point" considered is the calculation of the mean and variance standard deviation under the assumption of "linear combination of random variables and their independence". Let xi be from the "orange" overall x, let yi be from the "lemon" overall y, and x and y are independent of each other.

e(x) = 204 (g) and var(x) = (9 g) 2;e(y)=76(g), var(y)=(3g) 2, find the mean and standard deviation of z=3x+2y. According to the linear combination of random variables and their independence assumptions, e(z)=e(3x+2y)=3e(x)+2e(y)=764, var(z)=var(3x+2y)=9var(x)+4var(y)=729+36=761. Standard deviation of z = (761) (1 2).

FYI.