Question

For what value of k for which the quadratic equation 2x^2+ kx-8=0 has real roots

Answer 1

According to Quadratic formula :-

If D=0, polynomial will have equal real roots

If D>0, polynomial will have Unequal real roots

If D<0, polynomial will have Non-real roots.

Hence for the question D shud be either greater than or = 0. Taking the least required one.

Therefore ,

D = b2 - 4ac =0

= K2 - 4(2)(8) = 0

= K2 - 64 = 0

= K2 = 64

Hence K = +/- 8

Hence for the equation to have real roots , K shud be either greater than or equal to 8 or lesser than or equal to -8.