Khan/khan-exercises — Issue #9344: Functions 3 - keeping a negative...
Author: KhanBugz
Created: 2011-12-23 02:32:10+00:00
State: open
Labels: firefox, win7, wrong-or-unclear

Reporter: elijah.perez@gmail.com

h(x)=3x
g(x)=−x^3+3x^2−6x+3+5(f(x))
f(x)=−x^2−7x+2(h(x))

h(f(10))=?

First, let's solve for the value of the inner function, f(10). Then we'll know what to plug into the outer function.

f(10)=−10^2+(−7)(10)+2(h(10))

To solve for the value of f,we need to solve for the value of h(10).

h(10)=(3)(10)

h(10)=30

Okay, so h(10)=30.

That means f(10)=−10^2+(−7)(10)+(2)(30)

f(10)=−110

Except that without brackets, -10^2 should = 100 not -100
Otherwise it should be -(10^2)
which changes f(10) from 270 to -110...

no?

[functions_3.html?seed=102&problem=1](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/functions_3.html?seed=102&problem=1&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/functions_3.html?seed=102&problem=1&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5C%22270%5C%22%22%2C369%5D%2C%5B%22hint-activity%22%2C%220%22%2C719%5D%2C%5B%22hint-activity%22%2C%220%22%2C730%5D%2C%5B%22hint-activity%22%2C%220%22%2C735%5D%2C%5B%22hint-activity%22%2C%220%22%2C738%5D%2C%5B%22hint-activity%22%2C%220%22%2C740%5D%2C%5B%22hint-activity%22%2C%220%22%2C741%5D%2C%5B%22hint-activity%22%2C%220%22%2C745%5D%2C%5B%22hint-activity%22%2C%220%22%2C756%5D%5D)

["270"]

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:8.0) Gecko/20100101 Firefox/8.0

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