Binomial theorem formula

Binomial theorem formula

In binomial theorem, how to find CN several CN several. I know it is a quadratic term coefficient. Or I don't know what is a quadratic term coefficient
For example, what is the quadratic coefficient of (4 + 5) ^ n?

The coefficient of the term with the highest degree (that is, the second degree) in the equation is the quadratic term. Don't think it's so difficult. For example, the square of X in 0 = 2x + 4x + 2 is the quadratic term, and its coefficient is 2 (that is, the quadratic term coefficient)

How to solve the problems of [binomial coefficient sum] and [each coefficient sum] in binomial theorem and [what is the minimum term of expansion coefficient]

For the original small set 1 wealth value, detailed answers in the attachment!

What is the difference between binomial coefficient and term coefficient?

Binomial coefficient is just that combination number. Coefficient is a number that includes sign except unknown number

What quantifiers modify countable nouns?
What are the quantifiers that modify uncountable nouns
What quantifiers can modify both countable and uncountable nouns
What are the quantifiers that modify verbs
What are the classifiers that modify comparative degree

There is a detailed explanation about the modification of quantifiers, mainly about the modification of countable and uncountable nouns

Is y a function of X in the following formula? Why? (1) y = 3x-5 (2) y = X-2 / X-1 (3) y = √ X-1, please
This is the root sign

One is that two and three are not: the value range of X is not specified

I have some Chinese phrases. Can you translate them into English for me?
He has made a plan to set aside some money every month to travel to Beijing next year
Exercise can greatly improve your health
Keep an English dictionary at hand. When you can't understand a word correctly, you can look it up at any time
Please be sure to put out all the fires before leaving the camp
With the help of the mayor, we were finally allowed to contact the victims of the traffic accident
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Please translate as accurately as possible, I will add points! Thank you!

1.He has made plans,set aside some money every month,next year's trip to Beijing.2.Exercise can greatly improve your health.3.To English dictionary on hand,when you can not accurately understand a wor...

In △ ABC, D and E are points on BC and AC respectively, AE = 2ce, BD = 3CD, ad and be intersect at point F. if △ ABC = 12, what is the area of quadrilateral dcef

If eg ‖ ad is given to BC in G, then
DG/GC=AE/EC=2,
BD=3CD,
∴BF/BE=BD/BG=9/11,
∴S△BDF/S△BCE=BD/BC*BF/BE=3/4*9/11=27/44,
The area of quadrilateral dcef = (1-27 / 44) s △ BCE,
S△BCE/S△ABC=EC/AC=1/3,S△ABC=12,
∴S△BCE=4,
The area of quadrilateral dcef = 17 / 44 * 4 = 17 / 11

Why are some nouns after the plural and some singular
Briefly,

The is an article
It's a bag on the desk
There are also some special ones, such as adding the before Western musical instruments, rivers, coasts, mountains, islands, Straits, deserts, adding the before unique nouns in the world, and some fixed collocations
In fact, we have to contact the context

Let y = ax ^ 2 + BX + C, then y = ax ^ 2 + BX + C, then when x = X1 + X2, y = ax ^ 2 + BX + C=--------
I think the idea is right, but the result is strange

ax1²+bx1+c=0
ax2²+bx2+c=0
subtract
a(x1-x2)(x1+x2)+b(x1-x2)=0
x1≠x2
So divide both sides by x1-x2
a(x1+x2)+b=0
x1+x2=-b/a
So x = X1 + x2
y=a(-b/a)²+b(-b/a)+c
=b²/a-b²/a+c
=c