Can someone just check this to see if my answers are right, or if i'm on the right path?
consider the function f(x)=5x^2-17x+6

1. is the point (-7,132) on the graph of f?
my answer: 132= 5(-7)^2-17(-7)+6
132=370 answer: NO
2. find f(x) when x=8
f(8)=5(8)^2-17(8)+6
f(8)=178

3. find x when f(x)=7.75 (hint use the quadratic formula)
my answer: 7.75=5x^2-17x+6
0=5x^2-17x-1.75
a=5, b=17, c=-1.75
ends up to -17+18/10 or -17-18/10
=0.1 or -3.5

does any of this look right? any help would be great. thank you!

Question

Can someone just check this to see if my answers are right, or if i'm on the right path?
consider the function f(x)=5x^2-17x+6

1. is the point (-7,132) on the graph of f?
my answer: 132= 5(-7)^2-17(-7)+6
                     132=370 answer: NO
2. find f(x) when x=8 
f(8)=5(8)^2-17(8)+6
f(8)=178

3. find x when f(x)=7.75 (hint use the quadratic formula)
my answer: 7.75=5x^2-17x+6
    0=5x^2-17x-1.75
a=5, b=17, c=-1.75
ends up to -17+18/10 or -17-18/10
=0.1 or -3.5

does any of this look right? any help would be great. thank you!

anonymous · Answer

i think your second answer is incorrect

anonymous · Answer

am i supposed to find points on that one?

anonymous · Answer

nah i think you just made a mistake in your math, just try it again

anonymous · Answer

#2 Should be 190, the process is correct but the answer is wrong.

anonymous · Answer

f(8)=5(8)^2-17(8)+6
f(8)=320-136+6
f(8)=190  is that right?

anonymous · Answer

also your last answer has the wrong sign for 17, since the quadratic equation starts with -b

anonymous · Answer

yup 190 is correct

anonymous · Answer

oh your right!

anonymous · Answer

i mean you did apply -b, but your value for b was incorrect. it looks like you got everything now though

anonymous · Answer

but the answe is still the same bc -17 squares would be a positive number anyway right?

anonymous · Answer

yeah it doesnt change the value in the radical, but you need to look at the value before it, the -b plus or minus, b/c    -b  = -(-17) = 17

anonymous · Answer

again, you got the right process but, the designation of b should be -17

anonymous · Answer

oh. okay. i get it. duh! thank you

anonymous · Answer

glad you got it :) np

anonymous · Answer

therefore applying the formula $$-b \pm \sqrt{b ^{2}-4ac} all \over 2a$$

anonymous · Answer

okay here i am: 17+18/10=3.5 and 17-18/10=-0.1  i'm not getting that 1.1 you got?

anonymous · Answer

disrecard the *all please
that's right.
the answers are {3.5 and -0.1} only

anonymous · Answer

fabulous! thank you soo so much!

anonymous · Answer

just a typo error for the -
11/10

anonymous · Answer

no problem, ggodluck.

anonymous · Answer

does number 2 look right? 190 as the answer? for some reason i felt like i should have ponts x= (point,point) x=(point,point)

anonymous · Answer

*points

anonymous · Answer

no, 190 is correct, the problem is just asking what will be the value of f(x) when you substitute 8 to all the x's

anonymous · Answer

great! Thanks. life saver!

anonymous · Answer

you're welcome.