# basic algebra help!

• Jan 5th 2010, 09:42 AM
mike--1988
basic algebra help!
this is a simple question but its confused me
heres the question

f(x)= 2 - x^2 where x = -3

is it -7 or is it 11 im confused by the sign change

thanks..
• Jan 5th 2010, 09:46 AM
shinhidora
Quote:

Originally Posted by mike--1988
this is a simple question but its confused me
heres the question

f(x)= 2 - x^2 where x = -3

is it -7 or is it 11 im confused by the sign change

thanks..

\$\displaystyle f(x) = 2 - x^2\$ where \$\displaystyle x = -3\$
\$\displaystyle f(x) = 2-(-3)^2\$
\$\displaystyle f(x) = 2 - 9\$
\$\displaystyle f(x) = -7\$
• Jan 5th 2010, 09:46 AM
\$\displaystyle 3(3)=3+3+3=9\$

\$\displaystyle 3(-3)=-3-3-3=-9\$

\$\displaystyle (-3)(-3)=-[3(-3)]=opposite\ of\ subtract\ 3\ three\ times\$

\$\displaystyle which\ is\ add\ 3\ three\ times.\$

\$\displaystyle Hence\ (-3)(-3)=3(3)=9\$

\$\displaystyle 2-x^2=2-(-3)^2=2-(9)=-7\$
• Jan 5th 2010, 09:47 AM
bigwave
Quote:

Originally Posted by mike--1988
this is a simple question but its confused me
heres the question

f(x)= 2 - x^2 where x = -3

is it -7 or is it 11 im confused by the sign change

thanks..

f(-3) = 2 -(-3)^2 = -7
• Jan 5th 2010, 09:52 AM
mike--1988
thanks everyone (Rock)