Find the 4th term from the end in the expansion of (4x5−52x)9
TN=Tr+1=(−1)rnC2xn−ryr
4th term from the end 7th term from beginning
N=7,R=6,n=9,x=4x5,y=52x
T7=T6+1=(−1)69C6(4x5)3(52x)6
=9×8×73×2×r3×5653×26×x3x6
=9×8×7×536×x3=9×8×7×1256×x3
=10500x3