Answer
$10\sqrt {10}+14\sqrt {6b}$
Work Step by Step
Step 1: $8\sqrt {10}-4\sqrt {6b}+\sqrt {40}+9\sqrt {24b}$
Step 2: $8\sqrt {10}-4\sqrt {6b}+\sqrt {4\times10}+9\sqrt {4\times6b}$
Step 3: $8\sqrt {10}-4\sqrt {6b}+2\sqrt {10}+9(2)\sqrt {6b}$
Step 4: $8\sqrt {10}+2\sqrt {10}-4\sqrt {6b}+18\sqrt {6b}$
Step 5: $(8+2)\sqrt {10}+(-4+18)\sqrt {6b}$
Step 6: $10\sqrt {10}+14\sqrt {6b}$
