If we know the line L1: MX + NY + 4 = 0, L2: (m-1) x + y + n = 0, L1 goes through (- 1, - 1), ask whether L1 ‖ L2 holds? If it is true, find the value of M, N, if it is not true, explain the reason. (Science) vertex B (3, 4) of △ ABC, the linear equation of high CE on AB side is 2x + 3y-16 = 0, the linear equation of middle line ad on BC side is 2x-3y + 1 = 0, find the length of AC

If we know the line L1: MX + NY + 4 = 0, L2: (m-1) x + y + n = 0, L1 goes through (- 1, - 1), ask whether L1 ‖ L2 holds? If it is true, find the value of M, N, if it is not true, explain the reason. (Science) vertex B (3, 4) of △ ABC, the linear equation of high CE on AB side is 2x + 3y-16 = 0, the linear equation of middle line ad on BC side is 2x-3y + 1 = 0, find the length of AC

Substituting point (- 1, - 1) into L1, we get: - N-M + 4 = 0 ① When m = 1, n = 3, two straight lines are not parallel. When m ≠ 1, M-N (m-1) = 0 is obtained from L1 ‖ L2 ② Simultaneous solution of ① and ② leads to M = n = 2, where L1 and L2 coincide, so there is no linear Ce: 2x + 3y-16 = 0 for M and N, then the slope of AB is k = 32, and the linear AB: y-4 = 32 (x-3) 3x-2y-1 = 0 Let C (m, n), C be on the line Ce: 2x + 3y-16 = 0, then 2m + 3n-16 = 0, the midpoint D (3 + m2, 4 + N2) of BC be on the line ad: 2x-3y + 1 = 0, 3 + m-32 (4 + n) + 1 = 0, then C (5, 2).. AC = 16 + 1 = 17

1. In the triangle ABC, if the square of a = the square of B + the square of C = BC, find the value of A
2. Judge whether the following triangle ABC is an acute triangle, a right triangle, or an obtuse triangle
(1) A = 5, B = 12, C = 13 (2) a = 2, B = radical 2, C = radical 3 + 1 (3) a = radical 3, B = 2, C = radical 5
To write the process, I would like to thank you again

If the title is: B & sup2; + C & sup2; = 2bca & sup2; = B & sup2; + C & sup2;, is a right triangle, and B & sup2; + C & sup2; = 2BC, B & sup2; - 2BC + C & sup2; = 0, (B-C) & sup2; = 0, B = C ∠ a = 90 ° (1) a & S

Help me
The initial water consumption of a steel plant for producing one ton of steel is 25 tons, and the reuse rate of water is 20%. According to this calculation, the actual water consumption for one ton of steel production is 20 tons. In order to build a conservation oriented society and reduce the actual water consumption, the steel plant actively organized personnel to tackle key problems. After technical innovation, not only the initial water consumption of steelmaking is reduced. At the same time, the reuse rate of water is also improved. It is found that the reuse rate of water will increase by 2% when the initial water consumption is reduced by 0.2 tons (that is to say, one percentage point more than a% is a% + 1%). Thus, the actual water consumption rate of each ton of steel can be reduced to 16.8 tons.
(1) It is known that the water-saving technological innovation of the plant has been completed after three years of efforts, and the annual output before and after the technological innovation is the same. If the price factor is not taken into account, how many% of the annual water consumption of Chenbei after the technological innovation is lower than before?
(2) How much is the initial water consumption per ton of steel produced by the plant after the technological innovation
Don't talk nonsense like "monopoly military telescope"

Too hard% >_

In order to save water, a waterworks company adopts the following charging methods: if the monthly water consumption of each household is less than 10 tons, the charge for each ton of water is 2 yuan; if the monthly water consumption of each household is more than 10 tons, the charge for the excess part is 2.5 yuan per ton
1) In October, when Mr. Li paid 19 yuan for water, he used () tons of water at home
2) If Mr. Li uses a ton of water at home in November (a > 10), he should pay () yuan in November
3) Under the condition of (1) (2), if the water fee paid by Mr. Li's family in December is twice that of November, how many tons of water will be shared by Mr. Li's family in the fourth quarter (expressed by the algebraic formula containing a)

1) If not more than 10 tons, the maximum charge is 10 * 2 = 20 yuan. Mr. Li pays 19 yuan, so the water consumption is not more than 10 tons, and the water consumption is 19 / 2 = 9.5 tons. 2) if more than 10 tons, the water fee is 20 + 2.5 * (A-10) = 2.5a-5 yuan. 3) if the water fee paid in December is twice that in November, it is 5a-10 yuan