J's answer to Ken's Secondary 2 Maths Singapore question.
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The curve is symmetrical. The minimum point lies on the line of symmetry.
Both x-intercepts (which are mirror images of each other) are equidistant from the line of symmetry. So the midpoint between them lies on this line as well.
x-coordinate of the midpoint = (3 + 7)/2 = 10/2 = 5
This tells you that the line of symmetry has equation x = 5. Which means that the minimum point has an x-coordinate of 5 .
When x = 5, y = (5 - 3)(5 - 7) = (2)(-2) = -4
So the minimum point has coordinates (5,-4)
Both x-intercepts (which are mirror images of each other) are equidistant from the line of symmetry. So the midpoint between them lies on this line as well.
x-coordinate of the midpoint = (3 + 7)/2 = 10/2 = 5
This tells you that the line of symmetry has equation x = 5. Which means that the minimum point has an x-coordinate of 5 .
When x = 5, y = (5 - 3)(5 - 7) = (2)(-2) = -4
So the minimum point has coordinates (5,-4)
Date Posted:
3 years ago
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