Question #a01c5

1 Answer
Narad T.
Apr 15, 2017

The value of k is =84

Explanation:

For a perfect square, the discriminant Delta=0

for the quadratic equation

ax^2+bx+c=0

Here, we have

4x^2-32x-20+k=0

The discriminant is

Delta=b^2-4ac=32^2-4*4*(k-20)

32^2-16k+320=0

16k=1344

k=1344/16=84

So, the equation becomes

4x^2-32x-20+84=0

4x^2-32x+64=0

4(x^2-8x+16)=0

4(x-4)^2=0

(2(x-4))^2=0

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