Question

.

For what value of k is the expression
4x2 – 8x +k a perfect square?
A.
B.
C.
D.
E.
64
32
16
8
4.​

Answer 1

`k = 4`

Explanation:

Given

`4x^2 - 8x + k`

Required

Determine k if the expression is a perfect square

A quadratic is of the form;

`ax^2 + bx + c`

Where (by comparison):

`a = 4`
`b = 8`
`c = k`

If the above is a perfect square, then

`k = (b^2)/(4a)`

Substitute values for a, b and c

`k = (8^2)/(4*4)`

`k = (64)/(16)`

`k = 4`

Hence, k = 4