Year 12s: what will be the first way you research your future options? >>

Can someone explain why my graph is wrong? (sketching f(x) from f'(x))

Question (part d): http://prntscr.com/s97kn5

My diagram: http://prntscr.com/s97qmu

Diagram in textbook: http://prntscr.com/s97r0x

Reply 1

kubes_04

D is a negative cubic graph of f'(x) = -(x-2)(x+1)^2
so f(x) = −(x^4 - 6x^2 +8x)/4 + C
so your graph fits the pattern of being a negative quartic graph but I think your roots are wrong

(edited 3 years ago)

Reply 2

mqb2766

Original post by kubes_04

D is a negative cubic graph of f'(x) = -(x-2)(x+1)^2
so f(x) = −(x^4 - 6x^2 +8x)/4 + C
so your graph fits the pattern of being a negative quartic graph but I think your roots are wrong

f'(x) ~ -(x+2)(x-1)^2.
Looks like the book is wrong. From the very left f must be increasing as the gradient is positive.
If the book was -y, it would be similar to the OPs.