specialistt
19. What is the value of c so that x² – 11x + c is a perfect-square trinomial?
121
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specialistt
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ignore the 121 lol
amistre64
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well, a perfect square is of the form (a+b)^2, which expands out to:
a^2+2ab+b^2 lets compare that to what you are given
x^2 –11x + c
looks like a=x, and 2bx = -11x
id say b = -11/2
so c = b^2
specialistt
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i have worked it out and i cannot find the right answer.. the choices are,
121
121 over 4
-11 over 4
121 over 2
amistre64
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....
id say b = -11/2
so c = b^2
what praytell is (-11/2)^2 ?
timo86m
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is this completing the square?
specialistt
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-11/4?
amistre64
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no, -11/4
you got the /4 part right
now what is (-11)^2 ?
specialistt
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121/4.. im pretty sure that it!
amistre64
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\[\frac{-11}{2}*\frac{-11}{2}=\frac{(-11)^2}{(2)^2}\]
amistre64
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yes, that would be it :)
specialistt
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okay thank you soo much! XD