When the object moves in a straight line with uniform deceleration, the initial velocity is 3 M / s, the acceleration is the second power of - 0.4 m / s, and the displacement of the object passing through in a certain second is 0.4 M, How long has the object been moving before this second? Please write down the specific answer process

When the object moves in a straight line with uniform deceleration, the initial velocity is 3 M / s, the acceleration is the second power of - 0.4 m / s, and the displacement of the object passing through in a certain second is 0.4 M, How long has the object been moving before this second? Please write down the specific answer process

S = VT + 1 / 2at2, then s (T + 1) = V (T + 1) + 1 / 2 * a * (T + 1) 2-s (T)
=V-at-1 / 2 * t = 0.4, so t = 6S

The initial velocity of an object is equal to four meters per second, and the acceleration is equal to two meters per second
Displacement of an object in the first two seconds
The velocity of the object at the beginning of the third second

1、 The displacement in the first two seconds is s = v0t + (. 1 / 2) at ^ 2 = 4 × 2 + (1 / 2) × 2 × 2 ^ 2 = 16 (m)
2、 The speed of an object at the beginning of the third second is the speed of an object at the end of the second second
V2=V0+at=4+2×2=8（m/s）.

The acceleration direction is opposite to the initial velocity, and the magnitude is 0.5 meters per second
1. Take the direction of initial velocity as the positive direction, make the displacement time image of the object motion
2. Explain the significance of the slope of the curve when t = 0
3. Find out the point where the slope of the curve is equal to 0, and explain its meaning. What is the corresponding time?

1. It's too difficult to draw a parabola. When t = 1, the displacement is 1.75, when t = 2, it's 3, when t = 3, it's 3.75, and when t = 4, it's 4
2. Initial velocity
3 the velocity at this point is o

Let 4-digit. ABCD satisfy A3 + B3 + C3 + D3 + 1 = 10C + D, then the number of 4-digit is______ ．

A, B, C, D are natural numbers less than 10, ∵ A3 + B3 + C3 + D3 + 1 = 10C + D, ∵ A3 + B3 + C3 + D3 + 1 is a two digit number, ∵ a, B, C, D are natural numbers less than 5, ∵ if C = 1, d = 0, then a = 2, B = 0, then the four digit number is 2010, if C = 1, d = 1, then a = 2, B = 0, then the four digit number is 2011, if C = 1, d = 2, then a = 1, B = 1, then the four digit number is 2011 If C = 3, d = 0, then a = 1, B = 1, then the four digit is 1130, if C = 3, d = 1, then a = 1, B = 1, then the four digit is 1131, if C = 4, then C3 = 64, not in line with the meaning of the question, so the four digit may be: 2010 or 2011 or 1112 or 1130 or 1131

ABCD represents a four digit number, in which a, B, C and D are all one of 1, 2, 3 and 4, but they are different from each other. Please write down the total number of four digit ABCD satisfying a > b, b > C and C > D, and what are the numbers?
b> Change C to B

a>b,bd
When a is the largest, C is greater than B and D, but the size of B and D is not specified
So: 41324231
When C is the largest, a is greater than B. the size of D and a, B is unknown
So: 32413142243
5 in total

Let 4-digit. ABCD satisfy A3 + B3 + C3 + D3 + 1 = 10C + D, then the number of 4-digit is______ ．

A, B, C, D are natural numbers less than 10, ∵ A3 + B3 + C3 + D3 + 1 = 10C + D, ∵ A3 + B3 + C3 + D3 + 1 is a two digit number, ∵ a, B, C, D are natural numbers less than 5, ∵ if C = 1, d = 0, then a = 2, B = 0, then the four digit number is 2010, if C = 1, d = 1, then a = 2, B = 0, then the four digit number is 2011, if C = 1, d = 2, then a = 1, B = 1, then the four digit number is 2011 If C = 3, d = 0, then a = 1, B = 1, then the four digit is 1130, if C = 3, d = 1, then a = 1, B = 1, then the four digit is 1131, if C = 4, then C3 = 64, not in line with the meaning of the question, so the four digit may be: 2010 or 2011 or 1112 or 1130 or 1131

If the product ABCD of four mutually unequal integers a, B, C, d = 9, then the sum of these four integers is?
As long as the answer is (correct)

3×(-3)×1×(-1)=9
So sum = 0

If a + 3 out of 4 = B + 4 out of 5 = C + 6 out of 7 = D + 18 out of 19, which number is the largest in ABCD

A max
Take 1 / 4, 1 / 5, 1 / 7, 1 / 19 in turn

The quadrilateral ABCD is similar to a'b'c'd ', and a'B': b'c ': c'd': d'a '= 7; 8:11:14, if the perimeter of the quadrilateral ABCD is 40, find the sides of the quadrilateral ABCD

∵ quadrilateral ABCD ∵ quadrilateral a'b'c'd 'and
A'B':B'C':C'D':D'A'=7;8:11：14
∴AB:BC:CD:DA=7：8:11:14
And ∵ C quadrilateral ABCD is 40
∴AB=7,BC=8,CD=11,DA=14
I'm on a mission,

It is proved that for any given natural number n, there is always a four digit ABCD obtained from four digits of 1984, such that 7 | (n + ABCD)

Because: 7 | 1489 = 57 | 1498 = 07 | 1849 = 17 | 1894 = 47 | 1948 = 27 | 1984 = 37 | 9148 = 6, so that 7 | n = m, there is always 7 | ABCD = 7 - M. that is, there is always ABCD such that 7 | (n + ABCD) = 7 | (M + 7 - M) = 0