What is the equation? How to solve the equation? How to test? What is the equation solution? What is the equation solution? When answering these questions, the language should be a little concise, not too concise

What is the equation? How to solve the equation? How to test? What is the equation solution? What is the equation solution? When answering these questions, the language should be a little concise, not too concise

Let me explain one by one
What is an equation? An equation with unknowns is called an equation
How to solve the equation? According to the balance principle (i.e. how much is added on the left side of the equation, how much is added on the right side of the equation), or according to the relationship between the various parts of the equation, the term can be shifted (i.e. according to the divisor △ divisor = quotient, the divisor = divisor △ quotient is obtained)
What is the solution of the equation? The value of the unknown number that makes the left and right sides of the equation equal is called the solution of the equation
What is an equation solution? There is no "equation solution". Should it be an equation solution?
Solving an equation: the process of solving an equation
How to test? Replace the solution of the equation into the original equation, calculate the left and right sides of the equation respectively, and see whether the value on the left is equal to the value on the right. If it is equal, congratulations. The value of x you just calculated is correct
Example: 5 + x = 9
5+x-5=9-5………… Principle of balance (or x = 9-5) Move items according to the relationship between the parts in the formula)
x=4 ………… The solution of the equation
The above process is called solving the equation
Test: substitute x = 4 into the original equation
Left = 5 + 4 = 9, right = 9
Because the left side of the equation = the right side
So x = 4 is the solution of the original equation

(8 / 15 + 5 / 21) * 5 / 16 * 21 the short answer is 81 / 16

(8/15+5/21)*5/16*21
=8/15x5/16x21+5/21x21x5/16
=1/6x21+5x5/16
=7/2+25/16
=56/16+25/16
=81/16

In △ ABC, a = 5, B = 3, C = 120 °, then the value of sina: SINB is ()
A. 53B. 35C. 37D. 57

In △ ABC, sin asinb = AB = 53 can be obtained from sine theorem, so a

2009×20082008-2008×20092009=______ ．

2009×20082008-2008×20092009，=2009×2008×10001-2008×2009×10001，=0．

As shown in the figure, AB is the diameter of ⊙ o, CD is the chord, CN ⊥ CD and DM ⊥ CD are made through C and D respectively, and ab is intersected with N and m respectively. Will an and BM in the figure be equal, and explain the reason

Let o be op ⊥ CD in P. according to the vertical diameter theorem, PC = PD, ∵ cn ⊥ CD, DM ⊥ CD, ∵ DM ∥ op ∥ CN (two lines perpendicular to the same line are parallel), PC = PD, ∵ om = on (parallel line segments are proportional), OA = OB, ∵ ob-om = oa-on, that is BM = an

Using factorization calculation: 21 × 3.14 + 62 × 3.14 + 17 × 3.14 =?

3.14*（21+62+17）=314

As shown in the figure, it is known that in the triangle ABC, AB equals AC and ad bisectors BAC
(1) Triangle abd is equal to triangle ACD;
(2) BD equals CD

(1) Because ad is bisector BAC
So angle bad = angle DAC
It is also known from the title that ad = AC, ad is the common edge of the triangle abd and ACD
So, according to the edges and corners
Triangle abd is equal to triangle ACD
(2) Because the triangle abd is equal to ACD
So according to the principle of congruence
BD=CD

How to make a 90 degree elbow with a diameter of 44 cm with iron plate? The simpler the drawing, the better

Shrimp bend, 440mm is the middle diameter, plate thickness is 4mm, bending radius is 1.5 times of the diameter --- 660mm, a total of 4 bends, as shown in the figure: the expansion length of one section is 1382.3 (middle length), which are divided into 24 equal parts, left and right symmetrical, from the middle, the length of two sides are 350.3, 347.4, 338.5, 324.5, 306.4, 285.3, 262.5, 239.8, 218.7, 200.5, 186.6, 177.8, 174.8

What is the determinant of a matrix determinant?
Is it equal to the value of a layer of determinant? Adding is to add the determinant on the basis of the obtained number. In fact, it is still the determinant itself?

It's just to change the [] to the |, and then you can use the algorithm of determinant. The final result of determinant is a number, and the matrix is a matrix similar to a number table. The relationship between the two should be clear. I hope my answer is helpful~

85 degrees 30 minutes 18 seconds = () degrees 39.145 degrees = () degrees () minutes () seconds calculate 36 degrees 25 minutes 42 seconds + 107 degrees 52 minutes 31 seconds
85 degrees 30 minutes 18 seconds = () degrees 39.145 degrees = () degrees () minutes () seconds
Calculate 36 degrees 25 minutes 42 seconds + 107 degrees 52 minutes 31 seconds=
Five degrees, 17 minutes, 23 seconds by six=
120-38 degrees 41 minutes 25 seconds=
Divide 4 by 75 degrees=

Process: 30 minutes = 30 / 60 degrees = 0.5 degrees, 18 seconds = 18 / 3600 degrees = 0.05 degrees; 39.145 degrees = 39 degrees, 8 minutes and 42 seconds; process: 0.145 degrees = 0.145 * 60 minutes = 8.7 minutes, 0.7 minutes = 0.7 * 60 seconds = 42 seconds