Question

Sa se determine termenul al 4-lea al dezvoltari binomului la putere (x-3y) totul la 6

Answer 1

$\it T_4 = T_{3+1} = -C^3_6 x^{6-3} (3y)^6 = -C^3_6 x^3 \cdot3^6y^6 = -729\cdot C^3_6 x^3y^6$

$\it C^3_6 =\dfrac{6!}{3!(6-3)!} =\dfrac{3!\cdot4\cdot5\cdot6}{2\cdot3\cdot3!} = 20$

$\it T_4 = -729\cdot20x^3y^6 = -14580x^3y^6$