Question

Me ajudem a resolver estes dois exercícios, por favor?!

n(n-3)/2=14

n(n-3)/2=144

Answer 1

$a) \\ \\ \frac{n(n-3)}{2}=14\\ \\ n^2-3n=28\\ \\ n^2-3n-28=0\\ \\ \Delta=(-3)^2-4.1.(-28)=9+112=121\\ \\ x=\frac{3 \pm 11}{2}\\ \\ x_1=-4 \\ \\ x_2=7$

$\frac{n(n-3)}{2}=144\\ \\ n^2-3n=288\\ \\ n^2-3n-288=0\\ \\ \Delta=(-3)^2-4.1.(-288)=9+1152=1161\\ \\ x=\frac{3 \pm\sqrt{1152}}{2}$