Hi, 

x(2x+5)=168 

2x^2 + 5x - 168 = 0

Yes, factoring works: 

Coming up with the product of -8*21 = 168 and using that

(2x +21)(x -8) = 0  

(2x + 21)=0

x = -(21/10) = -10.5

(x -8) = 0 

x = 8 

The quadratic equations "always" works as well:







x = (-5 + 37)/4 = 8

x = (-5 -37)/4 = -42/4 = -21/2 = -10.5





 

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