Question

Multiply:​
$\left(i\right)$ $3a+4b-5c\text{and}3a$

Answer 1

Multiply $3a+4b-5c$ and $3a$

The multiplication of monomials can be performed by multiplication of their coeffficient and literals.

We have,

$(3a+4b-5c)\times \left(3a\right)$

$=(3a\times 3a)+(4b\times 3a)+(-5c\times 3a)$

$=(3\times 3)(a\times a)+(4\times 3)(a\times b)+(-5\times 3)(a\times c)$

$=9a^2+12ab-15ac$

$\therefore (3a+4b-5c)\times \left(3a\right)=9a^2+12ab-15ac$