This document discusses economic theories of production including isoquants, returns to scale, iso-cost lines, and conditions for output maximization. It begins by explaining properties of isoquants like shape, slope, and that higher isoquants represent greater output. It then defines constant, increasing, and decreasing returns to scale. Next, it introduces iso-cost lines as combinations of inputs that cost the same. Finally, it outlines the conditions for a firm to maximize output, which are for the isoquant and iso-cost lines to be tangent with a convex isoquant.