x2 + x - 20
x2+x-20 =x2+5x-4x-20 =x(x+5)-4(x+5) =(x+5) (x-4)
8a3 + 27b3
Given that, 8a3+27b3 =(2a)3+(3b)3 [a3+b3=(a+b) (a2-ab+b2)] =(2a+3b){(2a)2-2a×2b+(3b)2} =(2a+3b)(4a2-6ab+9b2)
a = 3+2 হয়, তবে প্রমাণ কর যে, a31a3=183
Given that, a =3+2 =1a=13+2=3-2(3+2)(3+2)=3-2(3)2-(2)2=3-23-2=3-21 ∴1a=3-2 ∴a+1a=3+2+3-2=23...........(i) now, a3+1a3=(a+1a)3-3a×1a(a+1a) =(23)3-3×23 =23×(3)3-63 =8×33-63 =243-63 =183 (proved)