Question

please give all the identities of chapter 2 class 9 cbse​

Answer 1

Standard Algebraic Identities List:

1.Identity I: (a + b)2 = a2 + 2ab + b2

2.Identity III: a2 – b2= (a + b)(a – b)

3.Identity IV: (x + a)(x + b) = x2 + (a + b) x + ab.

4.Identity V: (a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ca.

Answer 2

Answer:

(a+b)2=a2+2ab+b2  

(a−b)2=a2−2ab+b2

(a+b)(a–b)=a2–b2

(x+a)(x+b)=x2+(a+b)x+ab

(x+a)(x–b)=x2+(a–b)x–ab

(x–a)(x+b)=x2+(b–a)x–ab

(x–a)(x–b)=x2–(a+b)x+ab

(a+b)3=a3+b3+3ab(a+b)

(a–b)3=a3–b3–3ab(a–b)

(x+y+z)2=x2+y2+z2+2xy+2yz+2xz

(x+y–z)2=x2+y2+z2+2xy–2yz–2xz

(x–y+z)2=x2+y2+z2–2xy–2yz+2xz

(x–y–z)2=x2+y2+z2–2xy+2yz–2xz

x3+y3+z3–3xyz=(x+y+z)(x2+y2+z2–xy–yz−xz)

x2+y2=12[(x+y)2+(x–y)2]

(x+a)(x+b)(x+c)=x3+(a+b+c)x2+(ab+bc+ca)x+abc

x3+y3=(x+y)(x2–xy+y2)

x3–y3=(x–y)(x2+xy+y2)

x2+y2+z2−xy–yz–zx=12[(x−y)2+(y−z)2+(z−x)2]

hope it helps