Question
Question: \[x^{5} + 10x^{4}a + 40x^{3}a^{2} + 80x^{2}a^{3} + 80xa^{4} + 32a^{5} =\]...
x5+10x4a+40x3a2+80x2a3+80xa4+32a5=
A
(x+a)5
B
(3x+a)5
C
(−1)n/2(n+2)
D
(x+2a)3
Answer
(−1)n/2(n+2)
Explanation
Solution
Conversely
(x+y)n=n⥂C0+n⥂C1xn−1y1+n⥂C2xn−2y2+....+nCnx0yn(x+2a)5
=5⥂C0x5+5⥂C1x4(2a)1+5⥂C2x3(2a)2+5C3x2(2a)3+5⥂C4x1(2a)4+5⥂C5x0(2a)5
= x5+10x4a+40x3a2+80x2a3+80xa4+32a5.