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Mathematics 4 ESO – Unit 7 ELEMENTARY FUNCTIONS page 76 activity 6

a)  Watch the video on “Building a Quadratic Function” and answer:

  • I) What variable is represented by the letter “x”? And by the letter “y”?
  • II) How do we initially recognise the quadratic function?
  • III) The general form of the quadratic function is   y = ax2 + bx + c   What are the values of the variables “a”, “b” and “c” in this example?
  • IV) Why is the graph symmetrical?
  • What is the “vertex”? Where is it?
  • What three ways can we use to represent quadratic functions?

b)  Watch the video on “Quick Way of Graphing a Quadratic Function in Standard Form” and answer:

I) For the function y = –3x2 + 12x + 4

  • i) Find the axis of symmetry and draw it in a graph.
  • ii) Find the vertex and draw it.
  • iii) Find the values of y for: x=1 ; x=–1 ; x=2 and x=–2
  • iv) Draw the function.

II) Graph these functions:

  • i) 3x2 + 12x + 1
  • ii) x2 + x + 4
  • iii) –x2 – 5x + 7
  • vi) 2x2 – 6x – 1