q=(-2);\\
X_7=X_1\cdot q^{7-1}=X_1q^6=X_1\cdot q^4\cdot q^2=X_5\cdot q^2=(-\frac{1}{4}\cdot(-2)^2)=\\
=-\frac{1}{4}\cdot4=-1 " alt="X_n=X_1\cdot q^{n-1};\\
X_{10}=X_1\cdot q^{10-1}=X_1\cdot q^9=8;\\
X_5=X_1\cdot q^{5-1}=X_1\cdot q^4=-\frac{1}{4};\\
\frac{X_1\cdot q^9}{X_1\cdot q^4}= \frac{8}{- \frac{1}{4} } =-32;\\
q^5=-32=(-2)^5==>q=(-2);\\
X_7=X_1\cdot q^{7-1}=X_1q^6=X_1\cdot q^4\cdot q^2=X_5\cdot q^2=(-\frac{1}{4}\cdot(-2)^2)=\\
=-\frac{1}{4}\cdot4=-1 " align="absmiddle" class="latex-formula">