Polynomials | Exercise 2.1

Question 1

  1. The graphs of y=p(x)y = p(x) are given in Fig. 2.10 below, for some polynomials p(x)p(x). Find the number of zeroes of p(x)p(x), in each case.
Question diagram 1
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Solution

The number of zeroes of a polynomial is where its graph crosses the x-axis.

Step 1 — Understand zeroes

Let's look at the graphs. The zeroes are x-intercepts. These are points where y=p(x)=0y = p(x) = 0. We count how many times the graph touches or crosses the x-axis.

Diagram 1

Step 2 — Analyze graph (i)

The graph is a horizontal line. It is above the x-axis. It does not cross the x-axis.

Number of zeroes = 0\boxed{\text{Number of zeroes = 0}}

Step 3 — Analyze graph (ii)

The graph is a curve. It crosses the x-axis at three points. These are distinct points.

Number of zeroes = 3\boxed{\text{Number of zeroes = 3}}

Step 4 — Analyze graph (iii)

The graph is a curve. It crosses the x-axis at one point. This is a single point.

Number of zeroes = 1\boxed{\text{Number of zeroes = 1}}

Step 5 — Analyze graph (iv)

The graph is a parabola. It crosses the x-axis at two points. These are distinct points.

Number of zeroes = 2\boxed{\text{Number of zeroes = 2}}

Step 6 — Analyze graph (v)

The graph is a curve. It crosses the x-axis at four points. These are distinct points.

Number of zeroes = 4\boxed{\text{Number of zeroes = 4}}

Step 7 — Analyze graph (vi)

The graph is a curve. It crosses the x-axis at three points. These are distinct points.

Number of zeroes = 3\boxed{\text{Number of zeroes = 3}}

Answer

(i) 0 (ii) 3 (iii) 1 (iv) 2 (v) 4 (vi) 3

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