will fan and medal:
Which of the following is not a perfect square trinomial?

169 – 26y + y*2

81 + 18y + y^2

64 + 8y + y^2

25 + 10y + y^2

Question

will fan and medal:
Which of the following is not a perfect square trinomial?
   
169 – 26y + y*2

81 + 18y + y^2

64 + 8y + y^2

25 + 10y + y^2

welshfella · Answer

you need to find the square root of the first number and check if the coefficient of the term in x = 2* this square root ( note the root may be positive or negative) If this is the case then we have a perfect square.

welshfella · Answer

OH  - and the last term has to be y^2

ayonnaleflore · Answer

so my answer would be A??

welshfella · Answer

I notice that its y*2 in the first choice. Could that be a typo?

ayonnaleflore · Answer

yes its supposed to be y^2

welshfella · Answer

if its not a typo then one answer is A.

But there's another one which id not a perfect square.
Try the square root test on B , C and D.

welshfella · Answer

For B  for example  square root of 81  is 9   and 2*9 = 18 (  in '18x') so that is a perfect square trinomial

Get the idea?

welshfella · Answer

Try C
what is the square root of 64?

ayonnaleflore · Answer

8

ayonnaleflore · Answer

8x2=16

welshfella · Answer

ok so have we got a perfect square here?

ayonnaleflore · Answer

yes

welshfella · Answer

check 16 against the number thats in front of the term in x

ayonnaleflore · Answer

do you mean divide them????? 64/16=4

welshfella · Answer

No   what number multiplies x  inr multiplies y  in   64 + 8y + y^2
Sorry  i've been  writing x all the time when i should have written y!!.

welshfella · Answer

the number in fron of the y

welshfella · Answer

Its  8  right?   (8y)

welshfella · Answer

sorry  i've confused you

ayonnaleflore · Answer

its fine .......8*16 = 128????

welshfella · Answer

No  C is not a perfect square because  there is not a 16 infront of the middle term (the term ending in y) - its 8y . If it was a perfect square it would be 16y.

ayonnaleflore · Answer

ok so the answer is A???

welshfella · Answer

No the answer is C  We are looking for a triniomial which is not a perfect square.
A is a perfect square because SQuare root of 169 = -13  and  2*-13 = -26  which is the number in front of the term in y (middle term)

ayonnaleflore · Answer

oh......... ok i get it now 
thank you

welshfella · Answer

good yw

A will expand to

( y - 13)(y - 13)

- if we expand that we''ll  get y^2 - 26y + y^2

welshfella · Answer

* A will factor to

ayonnaleflore · Answer

ok got it