Question

Find the sum of $(4\sqrt{x}+6\sqrt{y})$ and $3(4\sqrt{x}-3\sqrt{y})$.

Answer 1

$(4\sqrt{x}+6\sqrt{y})+3(4\sqrt{x}-3\sqrt{y})$
$=4\sqrt{x}+6\sqrt{y}+12\sqrt{x}-9\sqrt{y}$ (By opening the brackets)
$=4\sqrt{x}+12\sqrt{x}+6\sqrt{y}-9\sqrt{y}$ (By re-grouping the like surds)
$=(4+12)\sqrt{x}+(6-9)\sqrt{y}$ (By adding and subtracting the like surds)
$=16\sqrt{x}-3\sqrt{y}$ .
$\therefore (4\sqrt{x}+6\sqrt{5})+3(4\sqrt{x}+3\sqrt{y})=16\sqrt{x}-3\sqrt{y}$ .