Homework Help

If f(x)=-2x^4+5 and g(x)=5x+1, what is f(-3)-g(3)?

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rosey-girl | Student, Grade 12 | (Level 1) Valedictorian

Posted November 8, 2012 at 4:35 AM via web

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If f(x)=-2x^4+5 and g(x)=5x+1, what is f(-3)-g(3)?

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durbanville | High School Teacher | (Level 1) Educator Emeritus

Posted November 8, 2012 at 5:01 AM (Answer #1)

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`f(x)= -2x^4 +5` and `g(x)= 5x+1`  so substitute for values of x

`therefore f(-3) - g(-3) = -2(-3)^4 + 5 - (5(-3) +1)`

= -2 (81) + 5 + 15 - 1  Take care with the symbols when you remove the brackets.

I see that I evaluated it using g(-3) my apologies. Therefore, g(3)should have been -(16) such that ....- (5 (3) +1)

-157 - 16= -173

So the answer as per "widowspeak" is -173

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widowspeak | (Level 1) Honors

Posted November 8, 2012 at 12:53 PM (Answer #2)

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The above answer is correct except they forgot to add 5 to evaluate f(-3):

f(-3) = -2*(-3)^4 + 5 = -162 + 5 = -157

g(3) = 5*3 + 1= 16

f(-3) - g(3) = -157 - 16 = -173

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