(3 - 4√2)(1 + 3√2) = a + b√2,
3 + 9√2−4√2−(4√2×3√2)=a+b√2
3 + 5√2−(4×3√2×√2)=a+b√2
3 + 5√2−(12×2)=a+b√2
3 + 5√2−24=a+b√2
-21 + 5√2 = a + b√2
Comparing both sides, we have b = 5