What is the equation of the line normal

Deangelo Hardy

Deangelo Hardy

Answered question

2022-04-08

What is the equation of the line normal to f(x)=(42x)2 at x=-3?

Answer & Explanation

oanhtih6

oanhtih6

Beginner2022-04-09Added 10 answers

Explanation:
First, find the point the normal line will intercept.
f(3)=(4+6)2=100
The normal line will pass through the point (-3, 100).
To find the slope of the normal line, we must first know the slope of the tangent line. The slope of the tangent line can be found through calculating f'(-3).
First, find f'(x). Through the chain rule,
f'(x)=2(4-2x)*(-2)=-4(4-2x)
The slope of the tangent line is
f'(-3)=-4(4+6)=-40
However, the normal line is perpendicular to the tangent line. Perpendicular lines have opposite reciprocal slopes. Thus, the slope of the normal line is the opposite reciprocal of -40 which is 140.
Relate the point the normal line intercepts, (-3, 100), and the slope of the line, 140, in an equation in point-slope form:
y100=140(x+3)

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