∑
Math Atelier
Home
Learn
Practice
Assessments
Worksheets
Videos
DE
Start practice
Home
→
Learn
→
Practice
→
Assessments
→
Worksheets
→
Videos
→
Start practice
DE
Calculus · SEC2_GYM
Curve analysis and optimisation
Foundation
Core
Stretch
Question 1/8
+12 XP
For
f
(
x
)
=
6
x
3
: what is the local slope at
x
=
1
?
Secant becomes tangent
f(x) = 6x³, x = 1
0
0.5
1
1.5
10
20
30
x
f(x)
Δx
Δy
(
1
,
6
)
slopes
f
(
x
)
=
6
x
3
Δx
=
0.6
→
m
=
30.96
Δx
=
0.3
→
m
=
23.94
Δx
=
0.1
→
m
=
19.86
Δy
Δx
=
f
′
(
1
)
=
18
curve f
secant Δx = 0.6
secant Δx = 0.3
secant Δx = 0.1
tangent, slope 18
point of tangency
All three secants pass through (1, 6). As Δx shrinks (0.6 → 0.3 → 0.1) the secant slope moves 30.96 → 23.94 → 19.86 — towards the tangent slope f′(1) = 18. That limit is the derivative.
Your answer
Hint 1/3
Check