D. first, eliminate B and C, because the highest degree in these two equation is 3, a 3-degree equation has 3 roots, not 4.
between A and D, A has the roots 0, 0, 7, and -7, all real roots.
D can be factored into (x²-49)(x²+1)=0 x²=49 or x²=-1 x=7 or -7, x=i or -i two real roots, two unreal roots
for the second equation: first, find the first term by using the formula: the nth term=the first term + (n-1)*difference you are given the 13th term and d=3.7 a13=a1+(13-1)d 1.9=a1+12*3.7 a1=-42.5
the sum of the first 13 terms is S=(a1+a13)*(13/2)=(-42.5+1.9)*6.5=-263.9
