If f(2x)=x^2+3x+9, find the value of 3f(4)-5 Thank you very much!
M mhv12345 New member Joined Feb 20, 2016 Messages 4 Feb 20, 2016 #1 If f(2x)=x^2+3x+9, find the value of 3f(4)-5 Thank you very much!
pka Elite Member Joined Jan 29, 2005 Messages 11,971 Feb 20, 2016 #2 mhv12345 said: If f(2x)=x^2+3x+9, find the value of 3f(4)-5 Click to expand... You are expected to show some of your own work so that we know how to direct help towards you. HINT \(\displaystyle f(4)=f(2\cdot 2)=~?\). Now show us what you think.
mhv12345 said: If f(2x)=x^2+3x+9, find the value of 3f(4)-5 Click to expand... You are expected to show some of your own work so that we know how to direct help towards you. HINT \(\displaystyle f(4)=f(2\cdot 2)=~?\). Now show us what you think.
D Deleted member 4993 Guest Feb 20, 2016 #3 mhv12345 said: If f(2x)=x^2+3x+9, find the value of 3f(4)-5 Thank you very much! Click to expand... Assume u = x/2 → f(u) = ? → f(4) = ? and so on... What are your thoughts? Please share your work with us ...even if you know it is wrong If you are stuck at the beginning tell us and we'll start with the definitions. You need to read the rules of this forum. Please read the post titled "Read before Posting" at the following URL: http://www.freemathhelp.com/forum/th...Before-Posting
mhv12345 said: If f(2x)=x^2+3x+9, find the value of 3f(4)-5 Thank you very much! Click to expand... Assume u = x/2 → f(u) = ? → f(4) = ? and so on... What are your thoughts? Please share your work with us ...even if you know it is wrong If you are stuck at the beginning tell us and we'll start with the definitions. You need to read the rules of this forum. Please read the post titled "Read before Posting" at the following URL: http://www.freemathhelp.com/forum/th...Before-Posting
M mhv12345 New member Joined Feb 20, 2016 Messages 4 Feb 20, 2016 #4 f(2x/2) = x2/2 +3x/2+9 f(x)=0.5x2+1.5x+9 3f(4)-5 2x=4 x=2 f(2) = 0.5(2)2+1.5(2) +9 =37 Right?
M mhv12345 New member Joined Feb 20, 2016 Messages 4 Feb 21, 2016 #5 y=2x f(y)=y^2+3x+9 3f(4)-5 =3[4^2+3(4)+9]-5 =106 106/2 = 53 correct?
M mhv12345 New member Joined Feb 20, 2016 Messages 4 Feb 21, 2016 #6 Denis said: I'm not paid to think... Click to expand... y=2x f(y)=y^2+3x+9 3f(4)-5 =3[4^2+3(4)+9]-5 =106 106/2 = 53 correct?
Denis said: I'm not paid to think... Click to expand... y=2x f(y)=y^2+3x+9 3f(4)-5 =3[4^2+3(4)+9]-5 =106 106/2 = 53 correct?
J jatinmaths New member Joined Mar 14, 2016 Messages 2 Mar 14, 2016 #7 Simple calculation f(2x)=x^2+3x+9, find the value of 3f(4)-5 Putting x=2 f(4)=4+6+9=19 So 3X19-5=52