Let the joint density of random variables X and y be f (x, y) = (1 / y) * e ^ - (y + X / y), x > 0, Y > 0

Let the joint density of random variables X and y be f (x, y) = (1 / y) * e ^ - (y + X / y), x > 0, Y > 0

（2x+y-1）²
（a+b）²-4（a+b+1）
4+12（x-y）+9（x-y）²
x³-9x
6xy²-9x²y-y³

(a + b) \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\y (...)

The coordinates of four vertices of parallelogram ABCD are a (5,7) B (3, x) C (2,3) d (4, x) to find X

The diagonals divide equally
So (7 + 3) / 2 = (x + x) / 2
x=5

Limx → 1 X-1 / X & # 178; - 1 for limit
I really don't have any points for the advanced mathematics questions

The parabola y = ax & # 178; + BX + C passes through the point (- 1,2) and the straight line y = X-1 and the intersection points B and C of X axis and Y axis. The analytic expression of this function is obtained
Complete solution step by step

In y = X-1, if x = 0, then y = - 1, if y = 0, then x = 1
That is to say, the coordinates of two points B and C intersecting with X and Y axes are (0, - 1) (1,0)
These two points are also on the parabola,
Substituting: - 1 = C A + B + C = 0
And then because the parabola passes the point (- 1,2)
a-b+c=2
The solution is a = 2, B = - 1, C = - 1
y=2x²-x-1

It takes 24 days for team a and team B to complete a project together. Now team B works alone for 10 days, and then team a and team B work together. As a result, it takes 4 days less than the original plan to complete the task (10 days for team B is not included). What percentage of the efficiency of team a is that of team B?

124 × 4 △ 10 = 160, 160 △ 140 (124-160) = 160 △ 140, = 150%. A: the efficiency of team a is 150% of that of team B

Complete the following experiments to measure the resistance of a small bulb. (1) to measure the resistance of a small bulb, according to the deformation formula of Ohm's law, just use the measured value

The tools used are: small light bulb, wire, two dry batteries, ammeter, switch key
Connect a series circuit, close the switch, read out the reading of the ammeter, and use the formula r = u / I to calculate the resistance of the small bulb

24ab^2c^2(a+b-c)-32abc(a-c-b)^2+8abc^3(c-a-b)

24ab^2c^2(a+b-c)-32abc(a-c-b)^2+8abc^3(c-a-b)
=8abc[3bc(a+b-c)-4(a-c-b)^2+c^2(c-a-b)]

Uncle Li deposits 8000 yuan into the bank for two years, with an annual interest rate of 2.07%. When it matures, how many yuan can Uncle Li get after tax interest?

8000*2.07%*2*（1-20%）=264.96

Several mathematical problems, tell the practical significance
1. Reduce the height by - 50 meters. 2. Income by - 1200 yuan. 3. Advance westward by - 58 meters

Height increased 50, loss 1200, eastward 58