Question

Could someone please answer question b) ii) ?
The question is on the attached image.

Answer 1

b) ii) The value of y when x is 2.5 is -1.5

How to find the value of y

b) ii) The value of y when x is 2.5 is read from the graph to be approximately -1.8

An mage is attached to show how to read the value.

This can be solved by substitution

For x = 2.5

y = (2.5)² - (2.5) - 3 = 1.75

Answer 2

b) i) Curve A

ii) - 1.75

iii) x = 1 - √5 or x = 1 + √5

Explanation:

b) i) We are given a function y = x² - 2x - 3 and the graph of this function is also shown in the side diagram.

The equation can be rearranged to y = (x - 1)² - 4

⇒ (x - 1)² = y + 4

Therefore, this is an equation of a parabola having the vertex at (1,-4) point and its axis is parallel to the positive y-axis.

So, the curve A represents the equation given. (Answer)

ii) Now, at x = 2.5, f(x) = 2.5² - 2 × 2.5 - 3 = - 1.75 (Answer)

iii) When y = 1, then x² -2x - 3 = 1

⇒ x² - 2x - 4 = 0

⇒ (x - 1)² - 5 = 0

⇒ (x - 1)² - (√5)² = 0

⇒ (x - 1 + √5)(x - 1 - √5) = 0

⇒ x = 1 - √5 or x = 1 + √5 (Answer)