Question 248159
Positive coefficient "a" means the curve opens upwards (like a cup sitting on a table). 
Large absolute value of a means "skinnier" graph compared to x^2 (green graph a=10).
Small absolute value of "a" means "wider" graph compared to x^2 (blue graph a=0.1).
{{{ graph( 300, 300, -5, 5, -10, 10, x^2, 10x^2, 0.1x^2) }}} 
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Negative coefficient "a" means the curve opens downwards. 

{{{ graph( 300, 300, -5, 5, -10, 10, -x^2, -10x^2, -0.1x^2) }}}