#(color(blue)(u)color(darkred)(+7v))(color(red)(u)color(green)(+7v))#
You proceed to FOIL it:
Where you multiply the #color(blue)"first term"# with the #color(red)"outer term"# then you multiply the #color(blue)"first term"# with the #color(green)"inner term"#:
#(color(blue)(u))(color(red)(u))=u^2#
#(color(blue)(u))(color(green)(7v))=7uv#
Now you multiply the #color(darkred)"last term"# with the #color(red)"outer term"# then you multiply the #color(darkred)"last term"# with the #color(green)"inner term"#:
#color(darkred)((7v))(color(red)(u))=7uv#
#color(darkred)((7v))(color(green)(7v))=49v^2#
Now combine them:
#u^2+7uv+7uv+49v^2#
Simplify:
#u^2+14uv+49v^2#
