Mathematics in the first year of junior high school, seeking the truth, solving the mathematics of t

Original = (1 10-1 11) + (1 11-1 12) + (1 12-1 13) +1 15-1 16) = 1 10-1 16 = 3 80, and the opposite number is -3 80It's the answer.

Original = (1 10-1 11) + (1 11-1 12) + (1 12-1 13) +1 15-1 16) = 1 10-1 16 = 3 80, and the opposite number is -3 80If there are multiple items after it and sum them, they are all equal to [1 10-1 The second half of the last term].

10x11] 1 = 1 10 -1 1111x12] 1 part = 1 11 - 1 12

3 80, the opposite number is -3 80

If you don't understand anything, you can ask again.

10*11/1 = 1 10-1 11

11x12 = 1 11-1 12

And so on The whole equation is 1 10-1 11 + (1 11-1 12) + (1 12-1 13) ......1/15-1/16）

Remove the parentheses and get the original = 1 10-1 16 = 3 80 and its opposite number is -3 80

1/n(n+1)=1/n-1/(n+1)

1/10x11 + 1/11 of 11x12 + 1/1 of 12x13 + 1/1 of 13x14 + ......15x16] is the opposite of one, which is -3 80

1 (n*(n-1))=1 n-1 (n+1) So after that it's 1 10-1 11+1 11-1 12+......1/15-1/16=1/10-1/16=16/160;So the opposite number is -(16 160) = -1 10

n*(n+1)1/1=1/n-(n+1)/1, the original formula =-[1/10-1/11 + 1-1/11/11 + ......1/15 - 1/16].

1/10-16].

3/80].

The inner angle of the regular n-sided shape is 180*(take the lack of n-2) n degrees, then m=10, the size of the inner angle is 144 degrees, and the inner angles of the two regular n-sided elimination shapes and the inner angles of one regular m-sided square are enclosed by 360 degrees, so that the inner angle of the regular n-sided shape is 108 degrees, and the calculable solution of 180*(n-2)=108 is n=5.

n=5。Because m=10, one of its internal angles is 180-360 m=144. One of the inner corners of the outer polygon is (360-144) 2=108, and its number of sides is 360 (180-108)=5.

So it is and n=5. Please rate.

n side row outer corner and 360

m=10, the coarse inner angle is 144 degrees.

The vertical mold of the inner horn rock in the shape of the n-sided fiber is (360-144) 2=108 degrees.

The outer angle is 72n = 5

n=5[m=10 internal fissures of the age of the horn of Lahu and 1440 each of the inner angles of 144, the remaining circumferential angle of 216

Each 216 has two figures, and the contiguous polygons are open to 108 inside angles

Pentagon 108 for each interior angle].

The angle of the m=10 is 180-360 m=144

Then the outer angle of the outer positive n deformation is 360-(hand hall 360-144) 2=72

So n=360 72=5

The conjecture be=ec, proves as follows:

d is the midpoint of ac, then ad=dc, and ac=2ab

ab=cd∠bae=90+45=135，∠edc=180-45-135∴∠bae=∠edc

Again ae=ed

abe≌△dce

be=ec

Prove the congruence of triangle AEB and triangle EDC, and the corner edge theorem.

Question 1: x=1 2 y=1

The first equation is multiplied by 2 on the left and right sides, and the two equations are added together) The second question: y>2

Multiply 6 on the left and right sides, and then move the term).

Solve the letters yourself and get a double the number, 7, 8, 9;11，12，13；24, 25, 26 [I'm not good at math, I don't care if it's right or wrong].

Hmm, since AB is parallel to CD, then BCD= ABC=46° EF is parallel to CD

CEF is complementary to ECD.

i.e. ecd=26°

bce=20°~

It's sauce (>

The internal angle of the same side is 180, the angle ECD=26, and the angle BCE=20 is obtained by using the internal wrong angle

(1) (x+x/x) squared = 16

x squared + 2 + x squared = 16

x squared + x squared = 14