Nilai dari ∑k=1a(6k−10)=....\sum_{k=1}^a\left(6k-10\right)=....∑k=1a(6k−10)=....
3a2−73a^2-73a2−7
3a2−7a3a^2-7a3a2−7a
a2−7aa^2-7aa2−7a
3a2+7a3a^2+7a3a2+7a
3a2−3a3a^2-3a3a2−3a