b = 19
substitute x = - [tex]\frac{4}{5}[/tex] into the equation and solve for b
5(- [tex]\frac{4}{5}[/tex])² - [tex]\frac{4}{5}[/tex] b + 12 = 0
[tex]\frac{16}{5}[/tex] + [tex]\frac{60}{5}[/tex] = [tex]\frac{4}{5}[/tex] b
[tex]\frac{76}{5}[/tex] = [tex]\frac{4}{5}[/tex] b
multiply both sides by 5 and divide by 4
b = [tex]\frac{76}{4}[/tex] = 19
