Chapter 291 (1/2)

Chapter 294

”you boy, you dismantle my platform as soon as you come back

Old Tang looked at standing by his side, obviously grew a lot of Cheng Nuo, could not help laughing and scolding.

Cheng Nuo hehe a smile, ”teacher, this is not for the sake of younger brother and younger sister, OK?”

Old Tang pushed to the side of the platform and left the stage to Cheng Nuo. He motioned to Cheng Nuo, ”start your performance.”

Under the gaze of more than 30 younger students and younger sisters, Cheng Nuo pulls out a piece of chalk and speaks loudly.

”There is no problem with the steps of proving this problem that Mr. Tang told you just now. So I didn't come up here to find fault. ”

”But, as you must see, the proof process of this subject is too complicated.”

Cheng Nuo uses a big circle to describe the whole blackboard. Then write a proposition in the corner.

As long as the initial six numbers are not even, odd, odd, even, odd, odd, and not all even, then we can make all the numbers equal to zero through finite operations. 】

Cheng Nuo tapped the blackboard with his fingers.

”It can be clearly seen that the formula of the blackboard, the classification discussion, are all proving this conjecture. If you're OK in your normal training and you have plenty of time, you'll have enough time to do it step by step. But in the competition, the time is competing for minutes and seconds, so this complex problem-solving process is not suitable

”Do you mean, senior, that you have a simpler proof process?” Chen Gong, a short boy sitting in the first row, raised his hand.

Chen Gong was sitting upright in his seat, looking up at Cheng Nuo, who was confident and eloquent on the stage, with a faint air of discontent in his eyes.

In the face of the younger brother's question, Cheng Nuo just laughed and nodded, ”yes, I did think of a simpler method of proof when listening to Mr. Tang speak about this topic just now.”

Chen Gong raised his hand again, ”senior student, the problem-solving method you use will not be the knowledge learned in the university?”

Cheng Nuo shook his head, ”it's not. To solve such difficult problems, the knowledge learned in high school is enough. ”

Cheng Nuo side, wipe off half of the blackboard, write three big characters on it.

Induction!

Induction, a very basic mathematical proof method in high school, is usually used to prove that a given proposition holds in the whole (or local) range of natural numbers. It can be divided into the first mathematical induction, the second mathematical induction, the backward induction and the spiral induction.

Seeing these three words on the blackboard, Chen Gong's eyes lit up and seemed to understand something, but his mind was still a blur.

As for the rest of the classroom, the expression is still confused. Isn't it about parity? How can we get to induction again.

As he wrote, Cheng told his thoughts.

“…… The steps in the previous part remain the same, resulting in the special value of 2. Later, we begin to prove this proposition by induction. The spiral induction method of induction is selected

”Generalize n, when n = 1, obviously Next, let A1 ≤ A2 ≤ Let Si = a1 + A2 + +ai。”

“…… To sum up, n satisfying the condition is 2 and all positive odd numbers. ”

The proof is over.

answers as like as two peas.

What's more, what's more terrifying is that Cheng Nuo only uses half of the blackboard and a dozen lines of formulas. It's a big difference from the proof formula filled with two blackboards before.

So terrible, so terrible!

Pa Pa Pa Pa Pa!

Standing on the side of the platform, old Tang raised his hands, clapped his hands, and looked at Cheng Nuo.