Date | November 2017 | Marks available | 5 | Reference code | 17N.1.hl.TZ0.6 |
Level | HL only | Paper | 1 | Time zone | TZ0 |
Command term | Solve and Hence or otherwise | Question number | 6 | Adapted from | N/A |
Question
Sketch the graph of y=1−3xx−2, showing clearly any asymptotes and stating the coordinates of any points of intersection with the axes.
Hence or otherwise, solve the inequality |1−3xx−2|<2.
Markscheme
correct vertical asymptote A1
shape including correct horizontal asymptote A1
(13, 0) A1
(0, −12) A1
Note: Accept x=13 and y=−12 marked on the axes.
[4 marks]
METHOD 1
1−3xx−2=2 (M1)
⇒x=1 A1
−(1−3xx−2)=2 (M1)
Note: Award this M1 for the line above or a correct sketch identifying a second critical value.
⇒x=−3 A1
solution is −3<x<1 A1
METHOD 2
|1−3x|<2|x−2|, x≠2
1−6x+9x2<4(x2−4x+4) (M1)A1
1−6x+9x2<4x2−16x+16
5x2+10x−15<0
x2+2x−3<0 A1
(x+3)(x−1)<0 (M1)
solution is −3<x<1 A1
METHOD 3
−2<1−3xx−2<2
consider 1−3xx−2<2 (M1)
Note: Also allow consideration of “>” or “=” for the awarding of the M mark.
recognition of critical value at x=1 A1
consider −2<1−3xx−2 (M1)
Note: Also allow consideration of “>” or “=” for the awarding of the M mark.
recognition of critical value at x=−3 A1
solution is −3<x<1 A1
[5 marks]