It is given that ∠ABC=900 and BM⊥AC as shown in the above figure:
Now with AM=8x2 and MC=2x2, consider,
BM2=AM×MC=8x2×2x2=16x4⇒BM=√16x4=4x2
Similarly, with AM=8x2 and MC=2x2, consider,
AB2=AC×AM⇒AB2=(AM+MC)×AM⇒AB2=(8x2+2x2)×8x2⇒AB2=10x2×8x2⇒AB2=80x4⇒AB=√80x4⇒AB=4x2√5
Hence, BM=4x2 and AB=4x2√5.