1×4/1+4×7/1+7×10/1…… +22×25/1+25×28/1=?

1×4/1+4×7/1+7×10/1…… +22×25/1+25×28/1=?

1×4/1+4×7/1+7×10/1…… +22×25/1+25×28/1=
=(1/3)[(1/1-1/4)+(1/4-1/7)+(1/7-1/10)+.+(1/22-1/25)+(1/25-1/28)]
=(1/3)(1-1/28)
=(1/3)*(27/28)
=9/28

1 and 3 / 1 * 4 + 3 and 3 / 4 * 7 + 5 and 3 / 7 * 10 +. + 17 and 3 / 25 * 28=

The original formula = (1 + 3 + 5 +...) +17）+（3/1*4+3/4*7+3/7*10+…… +3/25*28)
=9*(1+17)/2+[(1-1/4)+(1/4-1/7)+(1/7-1/10)+…… +(1/25-1/28)]
=9*9+(1-1/28)
=81 and 27 / 28

3 and 7 / 25 divided by 1.4

That is 82 / 25 divided by 1.4 = 82 / 25 divided by 7 / 5 = 82 / 35

What is 100 degrees, 2 minutes, 33 seconds - 14 degrees, 14 minutes, 53 seconds?

100°2'33''—14°14'53''
=99°62'33''—14°14'53''
=99°61'93''—14°14'53''
=85°47'40

How much is one-third minus one-quarter

One twelfth

What is positive 9 minus negative 3?

+9-(-3)
=9+3
=12

If t ≥ 3, the function between Y and t is

y=(t-3)×0.8+2.4
{if (T-3) is a decimal, take the integer part + 1}

Let f (x) be a periodic function with period equal to 2 and satisfy f (x) = x & sup2;, X belongs to (- 1,1]
Let f (x) be a periodic function with period equal to 2, and satisfy that f (x) = x & # 178;, X belongs to (- 1,1). For positive integer k, find the set MK = {a | such that the equation f (x) = ax about X has two unequal real roots in the interval (2k-1,2k + 1}

The function f (x) is a periodic function with period equal to 2
&Nbsp; & nbsp; f (x) = x & # 178;, X belongs to (- 1,1]
Let x ∈ (2k-1,2k + 1]
Then x-2k ∈ (- 1,1]
∴f(x)=f(x-2k)=(x-2k)²
The equation f (x) = ax, i.e. (x-2k) &# 178; = two unequal real roots of ax
Then f (x) = (x-2k) &# 178;, X ∈ (2k-1,2k + 1] image
&There are two intersections with the line y = ax
F (x) = (x-2k) &# 178;, X ∈ (2k-1,2k + 1] the image is a parabola arc,
The vertex is (2k, 0), the opening is upward, and the end of the arc is
AK (2k-1,1) & nbsp; (empty circle), BK (2k + 1,1) & nbsp; (real point)
 
If there are two intersections, then the line should be between the x-axis and obk
The slope of the line a is between 0 and the slope of obk
The slope of obk is 1 / (2k + 1)
 ∴0<a≤1/(2k+1)     
MK is the set of real numbers a which make the equation have two unequal real roots
That is, MK = (0,1 / (2k + 1)]

The period of the function y equals sin3x is t equals sin3x____ What is it____ (odd, even) function

T=2π/3
Odd function

How much is one thirteenth minus one thirteenth
Dear big brothers and sisters, is it equal to 0 / 3 or zero?

One thirteenth minus one thirteenth should be equal to zero thirteenth, but zero thirteenth is meaningless, so it is equal to zero