If both n and r be greater then 1, find the value of x if Δ=∣∣
∣
∣∣xCrn−1Crn−1Cr−1x+1CrnCrnCr−1x+2Crn+1Crn+1Cr−1∣∣
∣
∣∣=0
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Solution
Apply C3+C2 and note that n−1Cr−1+n−1Cr=nCr ∴Δ=∣∣
∣
∣∣xCrn+1CrnCrx+1CrnCrn+1Crx+2Crn+1Crn+2Cr∣∣
∣
∣∣ Now Δ=0 it two columns are identical. Comparing C1 and C3 we get x=n Comparing C1 and C2 we get x=n−1.