Answers to unit 9p70-2d textbook

Answers to unit 9p70-2d textbook

[answer] I'm glad to answer your question here. According to the text order, each line is: have, be, be, Southeast, speak, English, have ever watchhotel year

Who knows the answers of 2D and 2E in part B of English unit 1 of PEP eighth grade volume 1?

2d：went;Malaysia;did;family;sunny;paragliding;rode;father;was;waited;wet;umbrella;enough.
2e：was;went;started;saw;stopped;drank;walked;got;was;looked.

It is known that as shown in the figure, △ ABC and △ ade are equilateral triangles, point D is on side BC, EF / / BC intersects AC at point F, connecting be
Proof: quadrilateral befc is parallelogram

This is similar to your one. Have a look

Solid alcohol is smoke-free, pollution-free, high calorific value, easy to make and easy to use, which is very popular in hotels and field workers
(1) How much heat can be produced by burning 30g solid alcohol completely? (the calorific value of solid alcohol is 2.8 × 10 7 J / kg)
(2) If all the heat is absorbed by the water in the hot pot, how many kg20 ° C water can be heated to boiling at a standard atmospheric pressure?
(3) In practice, only about 1.8kg water at 20 ° C can be heated to boiling. What is the efficiency of the hot pot? Please put forward some suggestions to improve the efficiency

m=30g=0.03kg
Q=mq=0.03kg*2.8*10^7J/Kg=8.4*10^5J
Q suction = q discharge = 8.4 * 10 ^ 5J
M = q suction / C △ t = 8.4 * 10 ^ 5J / 4.2 * 10 ^ 3j / (kg ° C) * (100 ° C-20 ° C) = 2.5kg
Q suction = cm △ t = 4.2 * 10 ^ 3j / (kg ° C) * 1.8kg * (100 ° C-20 ° C) = 6.048 * 10 ^ 5
η = q suction / Q discharge = 6.048 * 10 ^ 5 / 8.4 * 10 ^ 5J = 72%

logx^2/3

It can be seen from the meaning that x > 0 and X ≠ 0, logx ^ 2 / 3

In triangle ABC, angle c = 90 degrees, CA = 10 cm, CB = 15 cm, find the area of square cdef

Let d be on AC, e be on BC and f be on ab. let CD = DF = EF = CE = x, then ad = 10-x and be = 15-x. from △ ADF ∽ Feb, ∧ (10-x): x = x: (15-x), then: (10-x) (15-x) = x & amp; sup2;, X & amp; sup2; - 25X + 150 = x & amp; sup2;, ∧ x = 6. S, and cdef = 6 & amp; sup2; = 36 (CM & amp; sup2;)

How to judge which resistance or bulb current the voltmeter is measuring in the circuit? It's better to have a diagram

A voltmeter can only measure the voltage of a resistor or the voltage of a bulb, not the current. It depends on which bulb or resistor the positive and negative terminals of the voltmeter are connected to. For example, a voltmeter and a lamp are connected in series (this is a wrong circuit, just to take an example)

If x belongs to N, x = 8-A, a belongs to N and X belongs to m, then the number of elements in M is at least several

10. A is a natural number, greater than 0
So x > 0, a > 0, 8-A > 0
0

Point C is the trisection point of line AB, point D is on line CB, CD: DB = 17:2, and cd-ac = 3. Find the length of line ab

If CD = 17x, then BD = 2x
Because C is the trisection of ab
So AC = BC / 2
So AC = 19x / 2
Because cd-ac = 3
So 17x-19x / 2 = 3
The solution is x = 2 / 5
So AB = 19x / 2) * 3 = 57 / 5
For reference! Jswyc

A invertible, prove adjoint matrix invertible!

A*=|A|A^-1
|A * | = ||a ^ - 1 | = |a ^ ^ n times |a ^ - 1 | = |a ^ (n-1)
Because a is invertible, the determinant of a is not zero
So | a | ^ (n-1) is not equal to 0
So | a * | is not equal to 0
So adjoint matrix is invertible