## which answer? is f(4) for f(x)=-x**2+5x-7 equal to 29 or -3?

Simplificatation, evaluation, linear equations, linear graphs, linear inequalities, basic word problems, etc.
dianeandjosh
Posts: 1
Joined: Thu Feb 10, 2011 3:10 am
Contact:

### which answer? is f(4) for f(x)=-x**2+5x-7 equal to 29 or -3?

Given :

f(x) = - x**2+5x-7 notice the - before the first term. This is ambiguous. It is a homework problem.

what is the value of f(4)? is it 29 or -3 ?

snowdrifter
Posts: 18
Joined: Tue Jan 11, 2011 4:52 pm
Contact:

Given :

f(x) = - x**2+5x-7 notice the - before the first term. This is ambiguous. It is a homework problem.

what is the value of f(4)? is it 29 or -3 ?

Here is why:
You function is $f(x)=-x^2+5x-7$
this makes $f(4)=-(4)^2+5(4)-7=-16+20-7=-3$

In other words the negative is not part of the variable being squared.
If you were meant to include the negative in the square the function would be: $f(x)=(-x)^2+5x-7$
Then $f(4)=(-4)^2+5(4)-7=16+20-7=29$

By the way, the common way of writing $x^2$ using just text is x^2.

SD