Known 1 1 ___ ＋___ ＝5 x y Find 3x + 2XY + 3Y ________________ 2x－xy＋2y Yes, come on. Thank you very much

Known 1 1 ___ ＋___ ＝5 x y Find 3x + 2XY + 3Y ________________ 2x－xy＋2y Yes, come on. Thank you very much

The numerator denominator is also divided by XY to get (3 / y + 2 + 3 / x) / (2 / Y-1 + 2 / x) = [3 (1 / x + 1 / y) + 2] / [2 (1 / x + 1 / y) - 1] = 17 / 9

Junior high school mathematics problems into my process
If x ^ 2n = 7, what is the value of (- 3x ^ 3n) ^ 2-12 (x ^ n) ^ 4?
I want to explain the process in detail

Original formula = 9 (x ^ 2n) & sup3; - 12 (x ^ 2n) & sup2;
∵x^2n=7
The original formula = 9 × 7 & sup3; - 12 × 7 & sup2;
=3087-588
=2499

Why do velocity and acceleration follow parallelogram rule?
Don't say it's because they are also vectors / vectors. Then, you can tell me why all vectors should follow the parallelogram rule, and don't say it's artificial. Then, you can tell me why they should be made into parallelograms. Isn't it OK for a circle

No way, because they are vectors
All vectors follow the parallelogram rule, which is not a man-made rule, but a rule found in long-term practice

Can a three digit number be divided by three? Just see if the sum of all digits of the number can be divided by three. Why? Is there such a rule for four digits?

All of them are OK, because all decimal systems start from 10, 10 divided by 3, more than 1100 divided by 3, more than 11000 divided by 3, more than 1200, more than 22000 more than 2, so add up their remainder, if it is a multiple of 3, it will be divisible

Monotonicity of function
The judgment method of function monotonicity

If f (x1) - f (x2) > 0, then f (x1) > F (x2) is an increasing function, and vice versa, then f (x1) > F (x2) is a decreasing function

On derivative
Let f (x) = e to the power of x-ax-1
(1) Finding monotone increasing interval of F (x)
(2) If f (x) increases monotonically in the domain R, the value range of a is obtained
(3) Is there a monotonic decreasing f (x) on (negative infinity, 0) and increasing f (x) on [, positive infinity)
3) Does f (x) monotonically decrease on (negative infinity, 0) and increase on (positive infinity, 0)? If there is a value of a, there is no reason

1.f`(x)=e^x-a
Let f '(x) > 0, then x > LNA
f`(x)

Why is the parallel vector A / / b a (x1, Y1) B (X2, Y2) x1y2-x2y1 = 0?
Explain

The so-called parallel vector is the vector that never intersects. We regard it as a system of equations of equivalent linear algebra
x1a1+y1a2=0
x2a1+y2a2=0
If x1, X2, Y1 and Y2 are constants and A1 and A2 are variables, then there is a determinant of matrix = 0 (because when determinant! = 0, there is only a definite solution (0,0), which intersects at the origin rather than parallel)
|x1,y1|
|x2,y2|=0.
So with x1y2-x2y1 = 0
It's over

Let X and y satisfy x26 + Y23 = 1, then the minimum value of X + y is______ ．

Let t = x + y, from x26 + Y23 = 1t = x + y, we get 3x2-4tx + 2t2-6 = 0, then △ = 16t2-4 × 3 (2t2-6) ≥ 0, the solution is - 3 ≤ t ≤ 3, the minimum value of X + y is - 3, so the answer is: - 3,

The first semester of the second grade
If you want to add, subtract, multiply, and not divide, you need 2000 more lanes

1+17
5*9
45*8
55*9
13*5+4
13+8*8
12*（1+6）
You can spell it yourself

When what is the value of integer a, the solutions X and y of the system of equations x + y = - 2,5x + 3Y = 2A are all negative?

Through this system of equations, we can get: x = 3 + A, y = - 5-a
If x and y are all negative, then we can easily get: 3-a