Z = e ^ xsiny, x = cosy, find DZ / Dy,

Z = e ^ xsiny, x = cosy, find DZ / Dy,

Z=e^sinycosy=e^(1/2sin2y)
dz/dy=[e^(1/2sin2y)]'=e^(1/2sin2y) * (1/2sin2y)'=e^(1/2sin2y) * cos2y

If z = the square of X - 3Y, then DZ=

dz=2xdx+3dy

Given x2 + xy = 3, XY + y2 = - 2, then the value of 2x2-xy-3y2 is ()
A. 12b. - 12C. 0d

∵ 2 (x2 + XY) - 3 (XY + Y2) = 2x2-xy-3y2, ∵ 2x2-xy-3y2 = 2 × 3-3 × (- 2) = 12

X2 + 4xy + 3y2 factorization,

x2+4xy+3y2
=(x+y)(x+3y)

There are 4 more girls than 23 boys in a class. If there are 3 fewer boys and 4 more girls, then the number of boys and girls is exactly the same. How many boys and girls are there in this class?

Suppose there are x boys, we can get the equation: 23x + 4 + 4 = x-3 & nbsp; 23x + 8 = x-3, & nbsp; & nbsp; & nbsp; 13X = 11, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 33.23 × 33 + 4 = 22 + 4, = 26. A: there are 33 boys and 26 girls

-How to do 5 (5x + y) - 3 (2x-3y)?

Hello: - 5 (5x + y) - 3 (2x-3y) = - 25x-5y-6x + 9y = 4y-31x ~ if you agree with my answer, please timely click the [adopt as satisfactory answer] button ~ ~ the mobile phone questioner can click [satisfied] in the upper right corner of the client. ~ your adoption is my driving force ~ ~ ~ if you have any new questions, please ask me for help

The number a is 120% of the number B, and how many% more than the number B
The number a is 25% of the number B, and the number B is what percentage of the number a

120% - 1 = 20%, so number a is 20% more than number B

What are the properties of nonnegative numbers?

1. Non negative numbers have square roots
2. The absolute value of a non negative number is still a non negative number
3. The square of a nonnegative number or a nonnegative number

The average number of a, B and C is 84. The ratio of a, B and C is 3:4:5. What are the numbers of a, B and C?

The sum of a, B and C is: 84 × 3 = 252, a number is: 252 × 33 + 4 + 5 = 63, B number is: 252 × 43 + 4 + 5 = 84, C number is: 252 × 53 + 4 + 5 = 105, answer: a number is 63, B number is 84, C number is 105

Mathematical problem solution: in a right triangle, if the sum of two right angles is 8, what is the maximum area of the triangle?

Let two right angle sides be x and Y respectively
Then x + y = 8
From the mean inequality, XY