Use the image below to answer the following questions:
Write an expression in expanded form for the area of the shaded region.
Write the expression for the area as a factorised polynomial.
Factorise the following expression by taking out the common factor:
Fully factorise $4b\left(4y+5x\right)+c\left(4y+5x\right)+3a\left(4y+5x\right)$4b(4y+5x)+c(4y+5x)+3a(4y+5x).
Factorise the following expression: