Add or subtract. Assume all variables represent non-negative real numbers.

Question

13√128 + 6√169 - 7√121 - 11√162

Answer 1

13√128 + 6√169 - 7√121 - 11√162
13√(64*2) + 6*13 - 7*11 - 11√(81*2)
13*8√2 + 78 - 77 - 11*9√2
104√2 + 1 - 99√2
1 + 5√2

don't just blindly copy and paste. There are no variables here, so that 2nd sentence is just noise.

Answer 2

Sum = 13*sqrt(64*2) + 6*13 - 7*11 - 11*sqrt(81*2),
Sum = 13*8*sqrt2 + 78 - 77 - 11*9*sqrt2
Sum = 104*sqrt2 + 1 - 99*sqrt2,
Sum = 5*Sqrt2 + 1 = 8.071.