13 / 27 * 8 + 19 / 27 * 13 =? Brothers and sisters, please! Tell me the answer! Hurry, hurry! ~ ~ ~ wuwuwu Today is the day! Ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah~~~~~~~~~~

13 / 27 * 8 + 19 / 27 * 13 =? Brothers and sisters, please! Tell me the answer! Hurry, hurry! ~ ~ ~ wuwuwu Today is the day! Ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah, ah~~~~~~~~~~

=13/27*8+13/27*19
=13/27*(8+19)
=13/27*27
=8

Factorization: the square of 3x - 2x + 4 is calculated by the formula: 25 / 17 × 47 / 19-30 / 17 × 25 / 19

This can't be broken down
25/17×47/19-30/17×25/19
=25/17×47/19-25/17×30/19
=25/17×(47/19-30/19)
=25/17×17/19
=25/19

1 / 2 + 1 / 5 + 1 / 7 + 1 / 9 + 1 / 11 + 1 / 13 + 1 / 15 + 1 / 17 + 1 / 19 = how to solve

1/2+1/5+1/7+1/9+1/11+1/13+1/15+1/17+1/19=
37826527 / 29099070
It can be calculated directly

X2Y2_ X2_ Y2+4XY+1

Problem solving principle: using the two commonly used formulas (a-b) ^ 2 = a ^ 2 + B ^ 2-2ab and (a + b) * (a-b) = a ^ 2-B ^ 2, divide 4xy into two 2XY forms, so as to work out the formula, and finally simplify it. This kind of "work together" method is often used in the future high school mathematics problem-solving, which is a skill that must be mastered
Details are as follows:
x2y2-x2-y2+4xy+1
=(x2y2+2xy+1)-(x2+y2-2xy)
=(xy+1)2-(x-y)2
=[(xy+1)+(x-y)]*[(xy+1)-(x-y)]
=(xy+x-y+1)(xy-x+y+1)
For the convenience of writing, the answer is in your writing form