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P(a≤X≤b)=∫abfX(x)dxP(X≤x)=FX(x)can be greater than 1 at a particular point
The probability of the X interval is equal to the probability of the Y interval (thin rectangle area)
fY(y)dy=fX(x)dxFor example
if
Y=X2,
fX=dydxfY and
dy=2xdx. Therefore
fY=2y1