1: If you put a 5kg object on the table 5 meters above the ground, please calculate its potential energy 2: 80% is represented by decimals and < > by fractions 3: Two times the difference between a number and 4, which is 42 times larger than half of the opposite number of this number, find this number 4: If x = 3 is a root of the equation x ^ - MX + 12 = 0, find the value of M and the other root < ^ is the square 5: If one day you eat melon seeds in the dormitory and accidentally drop the shell of melon seeds on the ground, the administrator just passes by and says "you are fined 30 yuan". You can't accept the cold attitude,

1: If you put a 5kg object on the table 5 meters above the ground, please calculate its potential energy 2: 80% is represented by decimals and < > by fractions 3: Two times the difference between a number and 4, which is 42 times larger than half of the opposite number of this number, find this number 4: If x = 3 is a root of the equation x ^ - MX + 12 = 0, find the value of M and the other root < ^ is the square 5: If one day you eat melon seeds in the dormitory and accidentally drop the shell of melon seeds on the ground, the administrator just passes by and says "you are fined 30 yuan". You can't accept the cold attitude,

1. Potential energy = mg △ H = 5 * g * 5 = 25g
(to understand the potential energy in this topic, we should also remember the formula of potential energy, potential energy = mg △ h, and sometimes pay attention to it
The unit of each quantity in this formula, the mass is absolute, the international unit is kg, and the value of acceleration will be given in the general question,
The international system unit is m / (s * s), the height is relative, the international system unit is m, if the unit is not international unit, remember
Convert the units
2.0.8 4/5
3. When solving this problem, we can set this number as X, and we can list the equation according to the problem
(x - 4) * 2 - (- x) / 2 = 42, x = 20
4. When solving this problem, we can assume that there are three possibilities
The equation B ^ 2-4ac > 0 has two unequal real roots
The equation B ^ 2-4ac = 0 has two equal real roots
B ^ 2-4ac 0, M > 4 radical 3 or m < - 4 radical 3
Bring a known root x = 3 into the equation
3 ^ 2 - 3M + 12 = 0, M = 7 (in accordance with the range of M obtained by the above formula)
Then M = 7 is brought into the equation, x ^ 2 - 7x + 12 = 0
The other root of the solution is x = 4
X = 3 and x = 4 are two unequal roots, which meet the hypothetical conditions
(2) Suppose the equation has two equal roots,
Then, B ^ 2 - 4ac = m ^ 2 - 4 * 12 = 0, M = 4 radical 3 or M = - 4 radical 3
But when m = 4 radical 3 or M = - 4 radical 3 is brought into the equation,
Then x = 3 is taken into the equation, which does not conform to the equation
(3) This equation already has a root, and the assumption that this equation does not have a real root does not hold
PS: this topic can not be so complicated, but in the future, we can consider it in this way
It's not easy to miss, and it's better to self check
5. Explain to the administrator that it's not intentional, and the administrator is not so unreasonable. The penalty is to pay attention to the security
Hold dormitory sanitation, say it well, then pick it up on your own initiative
I hope the above content can help you

Solution equation: (X-2) (x + 1) (x + 4) (x + 7) = 19

(x-2)(x+1)(x+4)(x+7)=19
(x+2.5-4.5)(x+2.5-1.5)(x+2.5+1.5)(x+2.5+4.5)=19
[(x+2.5)^2-4.5^2][(x+2.5)^2-1.5^2]=19
Note y = (x + 2.5) ^ 2
y^2-(45/2)y+(27/4)^2=19
(y-45/4)^2=100
Y = 85 / 4Y = - 5 / 4
X = (- 5 + √ 85) / 2 or x = (- 5 - √ 85) / 2

The function f (x) = (x ^ 2 + X + 1) e ^ x (x ∈ R) is an odd function defined on (- ∞, - 1] ∪ [1, + ∞), then the range of F (x) is

If it is a function in question, then: suppose that the function f (x) = (x ^ 2 + X + 1) e ^ x (x ∈ R) is an odd function defined on (- ∞, - 1] ∪ [1, + ∞). According to the definition of odd function, f (- x) = - f (x) is carried in and sorted out, x ^ 2 = - 1, x = ± I, that is to say, if the function is an odd function, then the function must be defined in the complex field Z

Use nine small squares with the side length of 1cm to make the following different figures. Calculate their perimeter respectively. 3,
What hasn't changed?

Hello: & nbsp; the first type: length = 9 cm, width = 1 cm, perimeter = (9 + 1) × 2 = 20 (CM) & nbsp; the second type: length = width = 3 cm, perimeter = 3 × 4 = 12 (CM) & nbsp; the (area) of the figure has not changed

1+1+2+3+4+5+6+7+8+9+8+7+6+5+4+3+2+1=?

You see it as three equations: 1 + 1, 2 + 3 + 4 + 5 + 6 + 7 + 8, 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1, and then you can quickly calculate the answer by adding them from both sides to the inside. 2, 35, 45, add these three numbers and you can wait until it is 82

Let the first term A1 of the sequence {an} be 1, and the first n terms and Sn satisfy the relation: 3tsn - (2t + 3) sn-1 = 3T (T > 0, n is natural number, n > = 2)
(1) Verification: the sequence {an} is an equal ratio sequence;
(2) Let the common ratio of the sequence {an} be f (T), and make the sequence {BN}, so that B1 = 1, BN = f {1 / (bn-1)} (n is a natural number, n > = 2),
Find the general formula of the sequence {BN}
Sn-1 is the sum of the first n-1 terms. Don't subtract 1 from the first n terms
Similarly, 1 / (bn-1) is the same

You can find the 18th question of this place by yourself. I can't post it
(1）∵3tSn－(2t＋3)Sn－1＝3t ①
∴3tSn＋1－(2t＋3)Sn＝3t ②
② - 1) 3T (Sn + 1-sn) - (2t + 3) (sn-sn-1) = 0
∴3tan＋1－(2t＋3)an＝0,∵t>0
∴
{an} is an equal ratio sequence with the first term A1 = 1 and the common ratio q = 1
(2）∵f(t)＝ ＝＋
bn＝f()
∴bn＝＋bn－1
∴bn－bn－1＝ (n≥2)
{BN} is an arithmetic sequence with the first term B1 = 1 and the tolerance d =. Then BN = 1 + (n-1) = (2n + 1)

The school needs 500 square bricks with a side length of 2 mm, and how many square bricks with a side length of 4 DM?

Suppose you need x bricks. According to the meaning of the question, 4 × 4x = 2 × 2 × 500 & nbsp; & nbsp; & nbsp; 16x = 2000 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 125 A: you need 125 such square bricks

Simple calculation: 3 / 8 + 2 / 5 - 3 / 8 + 2 / 5=

Three eighths + two fifths - three eighths + two fifths
3/8-3/8+（2/5+2/5
=4/5

Lim x --- > 1 / 1-x minus 1 / 3 of 1-x

1/(1-x)-1/(1-x)³=(x²-2x)/(1-x)³
Lim x --- > 1 / 3 of 1-x minus 1 / 3 of 1-x does not exist

The area of a circle is equal to that of a rectangle. The length of a rectangle is 18.84 cm. What is the radius of a circle?

The length a of the rectangle, the width b of the rectangle, and the radius r of the circle
πR²=ab
R = √ (AB / π) = √ (18.84b / 3.14) = √ (6b) (CM)