Answer 1

Here, we will use the identity​  \[\left( x - a \right)\left( x - b \right) = x^2 - \left( a + b \right)x + ab\].

\[\left( 3x - 4y \right)\left( 2x - 4y \right)\]

\[ = \left( 4y - 3x \right)\left( 4y - 2x \right) (\text { Taking common - 1 from both parentheses })\]

\[ = \left( 4y \right)^2 - \left( 3x + 2x \right)\left( 4y \right) + 3x \times 2x\]

\[ = 16 y^2 - \left( 12xy + 8xy \right) + 6 x^2 \]

\[ = 16 y^2 - 20xy + 6 x^2\]