exam Maths Puzzle Numerical Ability

How do you simplify. It is under Problem Set 4.1 number 47.

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exam Other Question

-N + 0.4N + 1.8 += 4.2 What is the transformational form of y= -1/3x^2+3x-1 ?
I got -3(y+23/4) =(x+9/2)^2 It was marked wrong :(