Question

The coefficient of x3 in (5 – 3x – 2x2)(x2 +7x) is
(a) -15
(b) -17
(C) 17
(d) 18​

Answer 1

$\huge\color{cyan}\boxed{\colorbox{black}{ANSWER ❤}}$

$(5 - 3x - 2 {x}^{2} )( {x}^{2} + 7x)$

$= 5 {x}^{2} + 35x - 3 {x}^{3} - 21 {x}^{2} - 2 {x}^{4} - 14 {x}^{3}$

$= 35x - 16 {x}^{2} - 17 {x}^{3} - 2 {x}^{4}$

So the coefficient of x³ is :

b) -17