1 x + y = k, X-Y = 20 (x, y are positive numbers) find the value of K 2, the solution of the equation 5x + 12 = 4A about X is negative, then the value range of a is? 1 Question 1 x + y = k, X-Y = 20 (x, y are positive numbers) to find the value of K In question 2, if the solution of the equation 5x + 12 = 4A of X is negative, then the value range of a?

1 x + y = k, X-Y = 20 (x, y are positive numbers) find the value of K 2, the solution of the equation 5x + 12 = 4A about X is negative, then the value range of a is? 1 Question 1 x + y = k, X-Y = 20 (x, y are positive numbers) to find the value of K In question 2, if the solution of the equation 5x + 12 = 4A of X is negative, then the value range of a?

x+y=K(1)
x-y=20(2)
(1) + (2) get
2x=k+20（3）
(1) - (2) get
2y=k-20（4）
From (3), we get x = 1,2k + 10
From (4), y = 1-2k-10
Because x > 0, Y0 1 / 2k-10 > 0
The solution is k > - 20, k > 20
So k > 20
Right?

The equation x ^ 2-6x-k = 1 has the same root as x ^ 2-5x-7 = 0. Find the value of K and the same root

Let the same root be m, the equation x ^ 2-6x-k = 1, the other root be a, the equation x ^ 2-5x-7 = 0, the other root be B, then M & # 178; - 6m-k-1 = 0, M & # 178; - 5m-7 = 0, M & # 178; - 6m-k-1 = M & # 178; - 5m-7 get m = 6-k, substituting M = 6-k into x ^ 2-5x-7 = 0, we can get: K & # 178; - 7k-1 = 0, the solution is: K1 = (7 + √ 53) /