The answer would be 16x^4
1) F + (N - 1)*D=Nth Term, where F=First term, D=Common difference and N=Number of terms.
-1 + (8 - 1)*D =20, solve for D
-1 + 7D = 20
7D = 20 + 1
7D =21 divide both sides by 7
D = 21 / 7
D = 3 Common difference
2)
(F + L) / 2*N, where F=First term, L=Last term and N=Number of terms.
Sum = (-7 - 115) / 2*13
Sum =( -122 / 2) * 13
Sum = -61 * 13
Sum = -793
79+43=122
122+58=180
so the answer is A 58
1. ([4.5*8]-4.5x)+36=102+([-2.5*3x]+[24*-2.5])
2. 36-4.5x+36=102-7.5-60
3. -4.5x/-4.5=52.5/-4.5
4. x=-13.125
a: -13.125