To find the point of intersection between the tangent line and the secant line, we first determine the equations of both lines.
Equation of the Tangent Line:
The given curve is y=ex. The derivative with respect to x is: dxdy=ex
At the point (c,ec), the slope of the tangent is: m1=dxdyx=c=ec
Using the point-slope form, the equation of the tangent line is: y−ec=ec(x−c)⟹y=ec(x−c+1)
Equation of the Secant Line:
The line joins the points (c−1,ec−1) and (c+1,ec+1). The slope of this secant line is: m2=(c+1)−(c−1)ec+1−ec−1=2ec(e−e−1)
Using the point (c−1,ec−1), the equation of the secant line is: y−ec−1=m2(x−(c−1)) y=2ec(e−e−1)(x−c+1)+ec−1
Finding the Point of Intersection:
Equating the two expressions for y: ec(x−c+1)=2ec(e−e−1)(x−c+1)+ec−1
Dividing the entire equation by ec: (x−c+1)=(2e−e−1)(x−c+1)+e−1
Let u=x−c. Then: (u+1)(1−2e−e−1)=e−1 (u+1)(22−e+e−1)=e1
Solving for u+1: u+1=e(2−e+e−1)2=2e−e2+12
Now, let us evaluate the denominator: 2e−e2+1=1−(e−1)2+1=2−(e−1)2
Since e≈2.718, we have: (e−1)2≈(1.718)2≈2.952>2
Therefore: 2e−e2+1<0
Since the numerator is positive (2>0) and the denominator is negative, we have: u+1<0⟹u<−1
Substituting back u=x−c: x−c<−1⟹x<c−1<c
Hence, the x-coordinate of the point of intersection satisfies x<c, which means the intersection lies on the left of x=c.