# কিছু প্রয়োজনীয় সুত্রঃ

# কিছু প্রয়োজনীয় সুত্রঃ
1. (a+b)²= a²+2ab+b²
2. (a+b)²= (a-b)²+4ab
3. (a-b)²= a²-2ab+b²
4. (a-b)²= (a+b)²-4ab
5. a² + b²= (a+b)² - 2ab.
6.a² + b²= (a-b)² + 2ab.
7. a²-b² =(a +b)(a - b)
8. 2(a² + b²) = (a+ b)² + (a - b)²
9. 4ab = (a + b)² -(a-b)²
10. ab ={(a+b)/2}²-{(a-b) /2}²
11. (a + b + c)² = a² +b² + c² + 2(ab + bc + ca)
12. (a + b)³ =a³ + 3a²b + 3ab² + b³
13. (a + b)³ = a³+ b³ + 3ab (a + b)
14. a-b)³=a³-3a²b+3ab²- b³
15.(a-b)³=a³- b³-3ab(a-b)
16. a³ + b³ = (a + b) (a² -ab+ b²)
17. a³ + b³ = (a+ b)³ -3ab(a + b)
18. a³ -b³ = (a -b) (a² + ab + b²)
19. a³-b³ = (a-b)³ + 3ab(a- b)