Graphs 7
3 marks · NormalUse the graph of to solve the equation .
Give your solutions to one decimal place.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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Also accept: Estimate values for x where y=3 intersects the given quadratic.
Common mistakes: Reading y=0 instead of y=3 intersection.
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Identifies method: y=3 means find intersection(s) of y=3 and the quadratic graph.
A1 · 1 mark · States first solution for x (to one decimal place, within 0.1).
A2 · 1 mark · States second solution for x (same tolerance). (follow-through)
Worked solution
Set y = 3: so x^2 - 2x - 1 = 3 → x^2 - 2x - 4 = 0.
From the graph, when y=3 the curve crosses at about x ≈ -1.2 and x ≈ 3.2.