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If #f(x) = 2x^2- x# , what is f(-3)?

Answer 1

Savannah Anderson

To find ( f(-3) ) when ( f(x) = 2x^2 - x ), substitute ( -3 ) for ( x ) in the function:

[ f(-3) = 2(-3)^2 - (-3) ]

[ f(-3) = 2(9) + 3 ]

[ f(-3) = 18 + 3 ]

[ f(-3) = 21 ]

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Answer 2

Eli Assouline

#f(-3)=21#

Put x = -3 into f(x) to evaluate f(-3)

#rArrf(color(red)(-3))=2(color(red)(-3))^2-(color(red)(-3))#

#=(2xx9)+3=21#

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Answer 3

Eli Assouline

#f(-3)=21#

For any function #f(x)# to find #f(a)# for a constant number #a#, we have just put #x=a# in #f(x)# and we get #f(a)#.

As #f(x)=2x^2-x#,

#f(-3)=2×(-3)^2-(-3)#

= #2×9+3#

= #18+3=21#

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.