Factorization: (a + b) square-9 [(a-b) square]

Factorization: (a + b) square-9 [(a-b) square]

Original formula = (a + b) square - [3 (a-b)] square
=[(a + b) + 3 (a-b)] [(a + b) - 3 (a-b)] (square difference formula, regarding (a + b) as a and 9 (a-b) as b)
=（4a-2b）(4b-2a)
=4(2a-b)(2b-a)

Factorization (Y-1) ^ 2 + 6 (1-y ^ 2) + 9 (y + 1) ^ 2

The original formula = (Y-1) & # 178; - 6 (y + 1) (Y-1) + 9 (y + 1) & # 178;
==[(y-1)-3(y+1)]²
=(-2y-4)²
=4(y+2)²

Factorization, given a (a + b) - B (a + 1) - A (a + 3) = - 9, find the value of 9a Λ 2 + B Λ 2 / 6 + ab

a(a+b)-b(a+1)-a(a+3)=-9
Party A + ab-ab-b-a - 3A + 9 = 0
3A+B=9
(3a + b) square = 81
9A + B + 6ab = 81
9A + B = 81-6ab
（9a∧2+b∧2）/6+ab=81/6=27/2

Calculation: 1-3 = - 2, 1-3 + 5-7 = (- 2) + (- 2) = - 4... According to the above rules: 1-3 + 5-7 + 9-11 +... - 2003 + 2005=

=-(2005+1)/2=-1003

There are two tunnels on the railway. It takes two minutes for the train to pass through the first tunnel and it takes two minutes to pass through the second one
A train with a total length of 800 meters runs at a speed of 72 kilometers per hour. There are two tunnels on the railway. It takes two minutes for the train to pass through the first tunnel and three minutes for the train to pass through the second tunnel. It takes six minutes for the train to enter the first tunnel from the front to leave the second tunnel from the rear. The distance between the two tunnels is two meters

The length of channel 1: (72 / 60) * 2-0.8 = 1.6km the length of channel 2: (72 / 60) * 3-0.8 = 2.8km the length from the head of channel 1 to the end of channel 2: (72 / 60) * 6-0.8 = 6.4km the distance

The circumference of the rectangle is cm, the length is am, and the width is () M
A. C-aB. C-2aC. C÷2-a

The width of rectangle: (C-2A) △ 2 = C △ 2-a

Given the function f (x) = 2 ^ X-2 ^ (- x), the sequence {an} satisfies f (log2 an) = - 2n. (1) the general term formula of the sequence {an}
f(log2 an) = -2n
=> 2^(log2 an)-2^(-(log2 an)) = -2n
=> an - 1/an = -2n
=> an^2 +2*n*an -1 = 0
=>An = - N + sqrt (n ^ 2 + 1) or an = - n-sqrt (n ^ 2 + 1)
Because there is logx an in the title, so an > 0, so we can only take the first one
an = -n+sqrt(n^2+1)
Why can 2 ^ (log2 an) - 2 ^ (- (log2 an)) = - 2n get an - 1 / an = - 2n

Your step is to use the following two common formulas
a^(log a n) =a
-(log a n) = log a (1/n)

On Sunday, his mother went to grandma's house. After walking for an hour, Xiao Ming found that he didn't bring the gift to grandma, so he immediately took the gift with him and rode a bicycle to chase after her. The lovely little dog also ran away with him. After catching up with his mother, he immediately returned to Xiao Ming, and then returned to chase after his mother. In this way, he kept running back and forth between them until Xiao Ming caught up with his mother, Xiaoming walks 12 kilometers per hour, and xiaohuagou's speed is 16 kilometers per hour. Can you calculate how many kilometers xiaohuagou ran when Xiaoming caught up with his mother?

The speed difference between mom and Xiao Ming is 12-4 = 8, that is to say, every one hour, Xiao Ming can catch up with mom by 8 kilometers. Here, mom walks for an hour and Xiao Ming goes to catch up, which means that Xiao Ming can catch up in half an hour, that is, 4 / (12-4) = 0.5. No matter how he runs, Xiao Hua dog only runs for half an hour, Its speed is 16 kilometers, half an hour, which is 8 kilometers

In rectangular ABCD, ab = 2, BC = 3, the side area of the geometry formed by rotating one circle around the straight line of BC side is______ ．

It can be seen from the meaning of the question that: in rectangular ABCD, the geometry obtained by rotating a circle around the straight line of BC side is a cylinder, and ∵ AB = 2, BC = 3, so the generatrix length of the cylinder is 3, the radius of the bottom circle of the cylinder is 2, so the side area of the cylinder is 2 π· 2 · 3 = 12 π. So the answer is: 12 π

(3-x) to the power of 0 = 1

3-x≠0
x≠3
Any number other than 0 to the power of 0 is equal to 1
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