The math problems in the second year of junior high school are very simple, but they need to be solv

If (x+2y)(2x+ny)=2 x to the 2nd power - mxy-6 y to the 2nd power, then m= n= the more detailed the content, the better, and I am helpless. Answer: You regard x and y as unknowns, then n and m are known numbers, which are the coefficients we have learned, and after the left equation, we can combine similar terms, we can know that n+4=-m, 2n=-6, n=-3, and bring in the previous equation to get:

3+4=Satisfied.

Solution: (x+2y)(2x+ny)=2x 2+nxy+4xy+2ny 2 (brackets) =2x 2+(n+4)xy+2ny 2 and the original formula=2x 2-mxy-6y 2 (known) m=n+4,-6=2n (by comparison) n=-3,m=-3+4=1 (solution of binary linear equations).

Left = 2x 2 + (4 + n) xy + 2ny

Right = 2x 2-mxy-6y 2

Because left = right.

So: 4+n=-m;

2n=-6n=-3;m=-1.

Left = 2x 2 + nxy + 4xy + 2ny 2 = 2x 2 + (n + 4) xy + 2ny 2

Right = 2x 2-mxy-6y 2

Look at the coefficient: n+4=-m

2n=-6, so n=-3

m=-1

The line segment between two points is the shortest.

So the minimum value of Pa+PB=distance of AB= (2-4) 2+(-2-1) 2= 13

(1) The cost of the school to the travel agency is y yuan, and there are x people in the team, and the equation y=360x (x 30) y=x[360-5(x-30)] x>30 and 360-5(x-30) 300 can be listed, that is, 30y=300x (x 42).

So, 20 360 = 7200

2) 360 30 = 10800 12400 300 42 = 12600 so 302 .Let d(x,y) because a, b, and c are all on the same inverse proportional function, so that all three points are y=k x (k is constant and k≠0), and we get 2(n+1)=(n-1)(n+4)=(-5-n)(n+5).

n=-3 is obtained

So the three points a(2,-2)b(-4,1)c(-2,2) form a parallelogram because the vertices a, b, c, and d form a parallelogram.

So the slope of the straight line ab and the straight line cd are equal, and ab=cd then x=4 y=-1

So, d(4,-1).

The area of the triangle is equal to 1 2*ac*bc, which is also equal to 1 2*cd*h

So h*5=3*4

h=, so choose b

Pick B. First, according to the Pythagorean theorem of a right triangle, the hypotenuse ab=sqrt(ac 2+bc 2)=5 is obtained from two right-angled edges, and then cd=ac*bc ab=3*4 5= is obtained according to the triangle area formula, s=

First, according to the Pythagorean theorem of a right-angled triangle, the hypotenuse ab = 5 is obtained from two right-angled edges, and then according to the triangle area formula, s=, cd=ac*bc ab=3*4 5= is obtained

Calculate how many tons of water is used first, and then calculate each ton**. Mountain cheats.

Set: The water used in December is x tons of absolute water. Solution: 18 x = (36 x + 6) (1 + 25%)

x = 10 tons;

18 10 = yuan tons (December last year).

36 (10+6)=36 16=yuan tons (January this year). Yuan.

Fake blind meditation set up a closed god round sedan collapsed in December last year with Y cubic meters of water.

Yes. xy=18x=