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jenejij
Group Title
If the graph of the quadratic function f(x) = x^2 + dx +3d has its vertex on the x axis what are the possible values of d? What if f(x) = x^2 + 3dx +1?
 2 years ago
 2 years ago
jenejij Group Title
If the graph of the quadratic function f(x) = x^2 + dx +3d has its vertex on the x axis what are the possible values of d? What if f(x) = x^2 + 3dx +1?
 2 years ago
 2 years ago

This Question is Closed

mukushla Group TitleBest ResponseYou've already chosen the best response.1
complete the square for x^2 + dx +3d to get its vertex
 2 years ago

meera_yadav Group TitleBest ResponseYou've already chosen the best response.1
mukushla is right :) try doing ...
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
I have the answers. Easily accessible in the back of the book. How to solve it is the problem. When you say complete the square what do you mean? I've been trying x^2 + dx +3d = ax^2 + (2ah)x+ (ah^2+k) And trying to identify the vertex.. that waayy... But what do you mean by complete the square?
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
the vertex of quadratic equation is given by (b/2a, cb^2/4a) since it has vertex on X axis therefore y ordinate =0 . hence cb^2=0
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
Thanks! I'll try it again.
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
in 1st case the value of d=0 and 3 in 2nd case d=1/3 and 1/3
 2 years ago

mukushla Group TitleBest ResponseYou've already chosen the best response.1
@jenejij take a look http://www.mathsisfun.com/algebra/completingsquare.html
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
Oh okay. I know how to "complete the square" haha. Got it. =)
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
Thanks everyone =)
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
Actually  still having problems.. =/ I don't think x=3. x= 0, and x= 12.
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
x=12 is not right answer
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
thats what the answer in the back of my text book is... but I don't know how to get there.
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
what is the final answer of first part?
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
d = 0 and d= 12. According the the textbook...
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
and for second part ??
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
\[d = + or  2 / \sqrt{13}\]
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
I got the answer: plz check it
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
the value of x coordinate of vertex is given by b/2a; from the given question we have a=1 b=d c=3d substituting the values in b/2a we have d/2
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
to find y ordinate substitute this value in the given eq. we have dw:1341572810912:dw
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
dw:1341572956794:dw
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
I circled that thing.. is it d?
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
since it has vertex on x axis thus y=0 hence we have d^2/4  d^2/2 +3d = 0 on solving we have d=0 and 12
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
yes it is d
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
have u understood ??
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
yes Thank you!!!
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
similarly u can do second part .. plz do it and tell me have u got the answer or not
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
okay I will work on it
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
give me a medal .........lol
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
\[x^2 + 3dx  d^2 +1 then 0 = (d/2)^2 +3d(d/2)  d^2 + 1 \]
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
\[(d/4)^2 + 3d^2/2 d^2 +1 = 0 \]
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
no; for second part u again need to find the x coordinate and follow the same steps
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
since it was a different equation
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
okay let me try again. toss that grain of salt my way (I've been working all night.. it's 4:21 am) I'm not usually this bad haha
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
no problem: from which country u r from ??
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
okay so then is 3d = b/2a?
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
I can't think. I have to do this in the morning. Thanks so far.
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
give me 1 min, let me tell you
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
in second part : a=1 b=3d c=1 now subs. in b/2a u have 3d/2
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
okay. I was on the right track. but not quite there.
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
then put this value of x in original equation x^2+3dx+1=0dw:1341574077931:dw
 2 years ago

jenejij Group TitleBest ResponseYou've already chosen the best response.1
Okay. I see the answer. And I understand, but without sleep I won't reeeally get it. Again thank you for your help.
 2 years ago

k.rajabhishek Group TitleBest ResponseYou've already chosen the best response.1
bye i had sent u mail plz check it
 2 years ago
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