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f'(x)=9x²​+4x, and f''(x)=18x+4 (derivatives) 

f'(x)=0 at x=0 or x=-4/9

when x=0 f''(x)>0 therefore a minimum value, when x=-4/9 f''(x)<0 and thus a maximum value. 

This is solving a quadratic equation. There are two ways we can solve this. Using the quadratic equation or completing the square. 1. Quadratic equation-The equation is in the form ax^2 + bx + c. Where a=...

Start by rearranging the inequality - make sure the sign next to the x² term is positive to make it easier: 

2x² -5x - 12< 0

Next step is to factorise this quadratic...

Times by 100

0.185 X 100= 18.5%

First make the denominator the same

3/10 X3 

2/15 X2

=9/30 + 4/30

=13/30