The graphs of the functions $f : x \mapsto |x|-3$ and $g : x \mapsto 2$ are shown in the diagram - Leaving Cert Mathematics - Question (b) - 2012
Question (b)
The graphs of the functions $f : x \mapsto |x|-3$ and $g : x \mapsto 2$ are shown in the diagram.
(i) Find the co-ordinates of the points A, B, C and D.
A = ( , )... show full transcript
Worked Solution & Example Answer:The graphs of the functions $f : x \mapsto |x|-3$ and $g : x \mapsto 2$ are shown in the diagram - Leaving Cert Mathematics - Question (b) - 2012
Step 1
Find the co-ordinates of point D
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Answer
Point D is where the graph of f(x) intersects the y-axis. At this point, x is 0.
Calculating:
f(0)=∣0∣−3=−3
Thus, the coordinates are D=(0,−3).
Step 2
Find the co-ordinates of point A
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Answer
Point A is where the graph f(x) intersects the line y=g(x).
Setting:
∣x∣−3=2
This simplifies to:
a) x−3=2⇒x=5
b) −x−3=2⇒x=−5
Calculating the y-coordinate for x=5:
A=(5,2).
Step 3
Find the co-ordinates of point B
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Answer
Point B is the intersection of the graphs at the coordinates where both functions are equal.
Setting:
∣x∣−3=2
Using:
x=1⇒B=(1,2).
Step 4
Find the co-ordinates of point C
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Answer
Point C is determined by solving the equation for g(x). Since g(x)=2 and occurs at x=3:
C=(3,2).
Step 5
Find the co-ordinates of point D
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Answer
Point D is where the graph of f(x) crosses the y-axis:
Using x=0:
g(0)=2
Thus:
D=(0,−3).
Step 6
Solve the inequality |x-3| < 2
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Answer
To solve the inequality:
∣x−3∣<2
This splits into two inequalities:
−2<x−3<2
Adding 3 to all sides:
1<x<5
Thus, the solution set is:
1<x<5.
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