Standard +0.3 This is a straightforward discriminant problem requiring students to recall that b²-4ac < 0 for no real roots, then solve a simple quadratic inequality. It's slightly above average difficulty for C1 as it involves an inequality rather than just finding roots, but remains a standard textbook exercise with a clear method.
Question 7:
7 | b2 −4ac soi
use of b2 −4ac < 0
k2 < 16 [may be implied by k < 4]
−4 < k < 4 or k > −4 and k < 4 isw | M1
M1
A1
A1 | may be implied by k2 < 16
deduct one mark in qn for ≤ instead of <;
allow equalities earlier if final inequalities
correct; condone b instead of k; if M2 not
earned, give SC2 for qn [or M1 SC1] for
k [=] 4 and − 4 as answer] | 4