Question

Express in the form of a complex number $a+bi$
$-(7-i)(-4-2i)(2-i)$

• A. $60-10i$
• B. $70-10i$
• C. $28-14i$
• D. $70-15i$

Answer 1

The correct option is B $70-10i$

Multiplying the given expression as follows:

$-\left[\right(7-i\left)\right(-4-2i\left)\right(2-i\left)\right]$

$=-\left[\right(-28-14i+4i+2i^2\left)\right(2-i\left)\right]$

$=-\left[\right(-28-10i-2\left)\right(2-i\left)\right]$

$=-\left[\right(-30-10i\left)\right(2-i\left)\right]$

$=-[-60+30i-20i+10i^2]$

$=-[-60-10+10i]$

$=-[-70+10i]$

$=70-10i$