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The square of B = AC is ()
B2 = AC is equivalent to a, ± B, C equal ratio sequence
So the square of B = AC is a sequence of a, B and C in equal proportion (necessary and insufficient condition)
What is the condition that "BB = AC" is "a, B, C are equal ratio sequence"?
If a, B and C are in equal proportion sequence
Then there must be BB = AC
If BB = AC, then a, B and C are not necessarily proportional
Because B = 0, a = 0
Then there is BB = AC, but it is not an equal ratio sequence
Therefore, it is necessary and insufficient
If a, B and C are known to be real numbers, then b * b = AC is the condition for a, B and C to be an equal ratio sequence?
If a = b = 0
Satisfy B & # 178; = AC
But it's not equal
So it's not enough
And the equal ratio must have B & # 178; = AC
It's necessary
So it is necessary and not sufficient condition
3.7-8 / 5 equals
2.1
Distance between a and B
The progress of the ship in still water is 24 km / h, and the current speed is 2 km / h. It takes 6 hours for the ship to travel back and forth between a and B. how long does it take for the ship to go downstream and upstream and how far is the distance between a and B?
X hours for downstream flow?
（24+2)x=(24-2)(6-x)
48x=132
x=2.75
6-x=3.25
（24+2)x=71.5km
Solution equation: 4 (2x-1) - 2 (x-1) = 22
The more detailed, the better!
4（2x-1）-2（x-1）=22
8x-4-(2x-2)=22
8x-4-2x+2=22
6x-2=22
6x=24
x=4
Given that a > 0, if three points a (1, - a), B (2, a ^ 2), C (3, a ^ 3) in the plane are collinear, what is a equal to?
Vector AB / / vector BC
That is, (1, a & # 178; + a) / / (1, a & # 179; - A & # 178;)
∴ a²+a=a³-a²
∵ a>0
∴ a+1=a²-a
∴ a²-2a-1=0
Ψ a = 1 + √ 2 (rounding off)
The sum of the two numbers is 35.76. Due to carelessness, I moved the decimal point of an addend one place to the left in the calculation, and the result is 23.61. What are the original two numbers
x+y=35.76
x+y/10=23.61
Calculated
x=22.26
y=13.5
A and B vehicles run from ab at the same time and meet for the first time at 80 km away from A. they arrive at each other's starting place and return immediately. On the way, they meet again at 60 km away from A. how many meters is the distance between AB and a?
Formula, equation,
Let AB be x km apart. When a walks 80, B walks x-80. When a walks (x-80) + (X-60), B walks 80 + 60
80/(x-80）=[(x-80)+(x-60)]/(80+60)
We get x = 150
There are several ways to classify rational numbers
Positive and negative numbers
Integers and fractions
Finite number and infinite circular decimal
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