When a curve "cuts the x-axis," it crosses the x-axis where y=0.
Set y=0:
0=(x−1)(x−2)(x−3)
A fraction equals zero only when its numerator is zero (and denominator is not zero).
x−3=0
x=3
The curve cuts the x-axis at the point (3,0).
To find the slope of the tangent at (3,0), find the derivative dxdy.
Given: y=(x−1)(x−2)(x−3)
Using the Quotient Rule: dxdy=v2u′v−uv′
Where:
- u=(x−3), so u′=1
- v=(x−1)(x−2)=x2−3x+2, so v′=2x−3
dxdy=[(x−1)(x−2)]21⋅(x2−3x+2)−(x−3)(2x−3)
Simplifying the numerator:
(x2−3x+2)−(x−3)(2x−3)
=x2−3x+2−(2x2−3x−6x+9)
=x2−3x+2−2x2+9x−9
=−x2+6x−7
At x=3:
Numerator: −(3)2+6(3)−7=−9+18−7=2
Denominator: [(3−1)(3−2)]2=[2×1]2=4
Slope =42=21
Using point-slope form with point (3,0) and slope m=21:
y−0=21(x−3)
y=21x−23
2y=x−3
2y−x+3=0
Therefore, the equation of the tangent is 2y−x+3=0.