The value of 50∑r=149 2r2−48r+1(50−r)⋅50Cr is _________.

∑r=149 2r2−48r+1(50−r)⋅50Cr=∑r=149 (r+1)2−r(50−r)(50−r)⋅50Cr=∑r=149 (r+1)2(50−r)⋅50Cr−r 50Cr=∑r=149 r+1(50−r) 50Crr+1−r 50Cr=∑r=149r+1(50-r)50!(50-r)!r!(r+1)-r50cr =∑r=149 r+1 50Cr+1−r 50Cr=50 50C50−1 50C1=50−150