The problem-solving process of (a-2b + 3C) & Seven under the colorful holiday life

（a－2b＋3c）²
=(a-2b)²+2(a-2b)×3c+(3c)²
=a²-4ab+4b²+6ac-12bc+9c²

RELATED INFORMATIONS

1. Given 4B = 3b, 2b = 3C, find a: B = (): () B: C = (): () a: C = (): () Given 4A = 3b, 2b = 3C, find a: B = (): () B: C = (): () a: C = (): ()
2. In the triangle ABC, a, B and C are the opposite sides of three internal angles a, B and C respectively, and a, B and C are not equal to each other. Let a = 4, C = 3 and a = 2C 1. Find the value of COSC 2. Find the value of B
3. Exponential formula is written as logarithmic formula: 4 ^ x = 1 / 6; 4 ^ x = 2. Please write the process. I just learned logarithm, Don't you have to write x = how much
4. 1. If two straight lines a and B are different, how can the plane passing through a and perpendicular to B not exist? I don't know. How can there be one? 2. The side of a pyramid is a triangle with a common vertex. If the side of a pyramid is an equilateral triangle, how many side triangles does the pyramid have at most? What is a triangle with a common vertex? What does it look like-
5. In △ ABC, a = 32 °, B = 81.8 ° and a = 42.9cm 2 in △ ABC, a = 20cm, B = 28cm, a = 40 ° to solve triangle 3 in △ ABC, a = 2 √ 3, C = √ 6 + √ 2, B = 60 ° to find B and a 4 in △ ABC, a = 134.6cm, B = 87.8cm, C = 161.7cm, solve triangle 5 in △ ABC, if a & sup2; = B & sup2; + BC + C & sup2;, then a =? 6 in △ ABC, if sinA:sinB If: sinc = 7:8:13, then C =? 7 in △ ABC, ab = √ 6 - √ 2, C = 30 °, then the maximum value of AC + BC is? 8 in △ ABC, if Asina + bsinb = csinc, what is the shape of △ ABC? 9 in △ ABC, prove a / B-B / a = C (CoSb / b-cosa / a)
6. In △ ABC, given AC = 16, area s = 220 √ 3, find the minimum value of A, Tick is the root sign Can someone tell me why everyone who answers the question says B = 16? How does that work out?
7. In △ ABC, it is known that the maximum internal angle a is twice of the minimum internal angle c, and the lengths of three sides a, B and C are three continuous positive integers, so the lengths of each side can be calculated
8. In the plane, three common point force vectors F1, F2 and F3 are in equilibrium. It is known that the module of vector F1 is 1n, the module of vector F2 is (radical 6 + radical 2) / 2n, and the angle between vector F1 and vector F2 is 45 degrees 1) Find the size of the vector F3 2) The angle between vector F1 and vector F3
9. What is the theorem of relation between root and coefficient
10. The theoretical and practical significance of Engel's coefficient
11. In △ ABC, ∠ C = 90 ° 4B2 + 3c2 = 43bc, can we find the degree of ∠ a? If you can, work it out. If you can't, explain the reason
12. Given that real numbers a, B, C satisfy a + C = 6-4b + 3B ^ 2, C-A = 4-4b + B ^ 2, then the size relation of ABC is
13. It is known that a, B and C are all nonnegative numbers and satisfy the equations 3A + 2B + C = 5 and 2A + b-3c = 1. If M = 3A + b-7c, the maximum and minimum values of M are obtained Tip: apply inequality knowledge.
14. 1+3+6+10+15+…… What's the law of life
15. 1 3 7 15 what are the six numbers in this order? What is the tenth number
16. The rule of number is: 1, 3, 6, 10, 15, 21. Find the difference between the 24th number and the 22nd number
17. There is a column of numbers: 1, 3, 6, 10, 15, 21... What is the nth number?
18. 1→3 2→6 3→10 4→15 5→21 … … The law of finding formula
19. 1. 2; 3; 4; 5; 6; 7. N 1; 2; 3; 4; 5; 6; 7 ........n 0; 1; 3; 6; 10; 15; 21 ........( )
20. Please observe the law of the following numbers and fill in the appropriate numbers in brackets according to the law: 1,2,3,5,8,13,21, (), 55,89?