\( 30 w ^ { 2 } - 5 l w + 9 \)

Did you know that quadratic expressions like \( 30w^2 - 5lw + 9 \) can represent various real-life situations? For instance, in architecture or design, this can model the surface area of a structure depending on width \( w \) and length \( l \). Such equations are pivotal in optimizing space and materials, making them fundamental in engineering projects! When working with quadratic expressions, a common mistake is not properly identifying the coefficients when factoring. Always double-check your signs and ensure you're recognizing which terms belong to which variable. It’s easy to overlook, but taking a moment to assess can save you from major errors down the line!