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Sketch on a single diagram the graphs of y = 5 - |x| and y = |2x – 3|. Hence, or otherwise, solve the inequality |2x-3|<5-|x|.

Mathematics

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a) (i) Sketch on a single diagram the graphs of y=5−∣x∣y = 5 - |x| and y=∣2x−3∣y = |2x - 3|.

To sketch the graphs, we identify key points and shapes for each function:

For y=5−∣x∣y = 5 - |x|:

  • If x≥0x \ge 0, y=5−xy = 5 - x. This is a line segment from (0,5)(0,5) to (5,0)(5,0).
  • If x<0x < 0, y=5−(−x)=5+xy = 5 - (-x) = 5 + x. This is a line segment from (0,5)(0,5) to (−5,0)(-5,0).
  • The graph is a V-shape opening downwards, with its vertex at (0,5)(0,5). It passes through (−5,0)(-5,0), (0,5)(0,5), and (5,0)(5,0).

For y=∣2x−3∣y = |2x - 3|:

  • The critical point is where 2x−3=02x - 3 = 0, which is x=32x = \frac{3}{2}.
  • If x≥32x \ge \frac{3}{2}, y=2x−3y = 2x - 3. This is a line segment starting from (32,0)(\frac{3}{2},0). For example, it passes through (2,1)(2,1) and (3,3)(3,3).
  • If x<32x < \frac{3}{2}, y=−(2x−3)=−2x+3y = -(2x - 3) = -2x + 3. This is a line segment ending at (32,0)(\frac{3}{2},0). For example, it passes through (0,3)(0,3) and (1,1)(1,1).
  • The graph is a V-shape opening upwards, with its vertex at (32,0)(\frac{3}{2},0). It passes through (0,3)(0,3), (32,0)(\frac{3}{2},0), and (3,3)(3,3).

The intersection points of the two graphs are found by setting 5−∣x∣=∣2x−3∣5 - |x| = |2x - 3|.
Case 1: x<0x < 0
5+x=−(2x−3)5 + x = -(2x - 3)
5+x=−2x+35 + x = -2x + 3
3x=−2  ⟹  x=−233x = -2 \implies x = -\frac{2}{3}.
y=5−∣−23∣=5−23=133y = 5 - |-\frac{2}{3}| = 5 - \frac{2}{3} = \frac{13}{3}. Intersection point: (−23,133)(-\frac{2}{3}, \frac{13}{3}).

Case 2: 0≤x<320 \le x < \frac{3}{2}
5−x=−(2x−3)5 - x = -(2x - 3)
5−x=−2x+35 - x = -2x + 3
x=−2x = -2. This is outside the interval 0≤x<320 \le x < \frac{3}{2}, so no intersection here.

Case 3: x≥32x \ge \frac{3}{2}
5−x=2x−35 - x = 2x - 3
8=3x  ⟹  x=838 = 3x \implies x = \frac{8}{3}.
y=5−∣83∣=5−83=73y = 5 - |\frac{8}{3}| = 5 - \frac{8}{3} = \frac{7}{3}. Intersection point: (83,73)(\frac{8}{3}, \frac{7}{3}).

a) (ii) Hence, or otherwise, solve the inequality ∣2x−3∣<5−∣x∣|2x - 3| < 5 - |x|.

We need to solve the inequality ∣2x−3∣<5−∣x∣|2x - 3| < 5 - |x|. We consider the same cases as for the intersection points.

Case 1: x<0x < 0
The inequality becomes −(2x−3)<5−(−x)-(2x - 3) < 5 - (-x):
3−2x<5+x3 - 2x < 5 + x
−2<3x-2 < 3x
x>−23x > -\frac{2}{3}
Combining with x<0x < 0, the solution for this case is −23<x<0-\frac{2}{3} < x < 0.

Case 2: 0≤x<320 \le x < \frac{3}{2}
The inequality becomes −(2x−3)<5−x-(2x - 3) < 5 - x:
3−2x<5−x3 - 2x < 5 - x
−2<x-2 < x
Combining with 0≤x<320 \le x < \frac{3}{2}, the solution for this case is 0≤x<320 \le x < \frac{3}{2}.

Case 3: x≥32x \ge \frac{3}{2}
The inequality becomes 2x−3<5−x2x - 3 < 5 - x:
3x<83x < 8
x<83x < \frac{8}{3}
Combining with x≥32x \ge \frac{3}{2}, the solution for this case is 32≤x<83\frac{3}{2} \le x < \frac{8}{3}.

Combining the solutions from all three cases:
(−23<x<0)∪(0≤x<32)∪(32≤x<83)(-\frac{2}{3} < x < 0) \cup (0 \le x < \frac{3}{2}) \cup (\frac{3}{2} \le x < \frac{8}{3})
This simplifies to the interval between the two intersection points:

−23<x<83-\frac{2}{3} < x < \frac{8}{3}

The solution to the inequality is −23<x<83\boxed{-\frac{2}{3} < x < \frac{8}{3}}.

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