3x + 4y = 2 ②

For example, the above equations, ① and ② can be marked directly in the place given by the topic. Next, in order to calculate x, you should perform the following steps:

②-①*4: 3x-2x * 4 = 2- 1 *4 (because y has been eliminated).

-5x = -2

X = 2/5 (or 0.4)

Then substitute x into formula ① or ②, that is, y = 1/5 (or 0.2).

Finally, x = 0.4 and y = 0.2 return to the original equation. If they are all true, the result is correct.

You can write the following sentences:

After testing, the solution of the equation is x = 0.4 and y = 0.2 (of course, you should enclose it in braces).

Similarly, for example, in the title, ray OD is the angular bisector of ∠AOB, and ray OE is the angular bisector of ∠BOC.

Then you can answer like this:

∫ Ray OD is the angular bisector of∝∠ ∝∠AOB.

∴∠AOD = ∠BOD

The same reason ∠BOE = ∠COE (you can use it again here, only one more sentence, but if the topic is very complicated, the same reason is particularly important)

The following questions are about "summary". For example, the title says: ∠ AOB = 45, ∠ AOC = 30, then ∠BOC is equal to how many degrees?

Obviously, this should be considered in two cases: 1. B and c are on the same side of AO, then ∠ BOC = 15.

2. If B and C are opposite to AO, then ∠ BOC = 75.

To sum up, ∠ BOC = 15 or 75.

The use of "summary" refers to more than one situation of the topic. You should learn to judge for yourself. When you list all possible situations, add "summary" at the end to give your answer, so that you can find your answer clearly when marking the paper. Generally, the answers are right, and the process will not be so careful (when marking papers).

All the above are personal opinions. Please correct me if there are any mistakes. Thank you!