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peekaboopork
Group Title
How to determine the value of k of the trinomial that is a perfect square?
9x^2 + kx + 49
 one year ago
 one year ago
peekaboopork Group Title
How to determine the value of k of the trinomial that is a perfect square? 9x^2 + kx + 49
 one year ago
 one year ago

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ParthKohli Group TitleBest ResponseYou've already chosen the best response.1
Recall that \((3x + 7)^2 = 9x^2 + \cdots+49\).
 one year ago

ajprincess Group TitleBest ResponseYou've already chosen the best response.3
If \(ax^2+bx+c\) is a perfect square then \(b=2*\sqrt a*\sqrt c\) here a=9 and c=49 Does that help @peekaboopork
 one year ago

mathstudent55 Group TitleBest ResponseYou've already chosen the best response.0
(a + b)^2 = a^2 + 2ab + b^2 9x^2 = (3x)^2 49 = 7^2 (3x + 7)^2 = 9x^2 +42x + 49 (3x  7)^2 = 9x^2  42x + 49 k = 42 or k = 42
 one year ago

ParthKohli Group TitleBest ResponseYou've already chosen the best response.1
A good way to find the middle term is to realize that in a perfect square, \(2ab\) is the middle term where \((a +b)^2 = a^2 + 2ab + b^2\). Here, \(b^2= 49 \iff b = 7\) and \(a^2 = 9x^2 \iff a = 3x \).
 one year ago

ParthKohli Group TitleBest ResponseYou've already chosen the best response.1
So what would \(2\cdot 7\cdot 3x\) be?
 one year ago

ParthKohli Group TitleBest ResponseYou've already chosen the best response.1
Actually I should have put \(\pm\), but it still would have the same result!
 one year ago
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