(1) x4+4=(x2+2)2−4x2=(x2+2x+2)(x2−2x+2)x^4 + 4 = (x^2 + 2)^2 - 4x^2 = (x^2 + 2x + 2)(x^2 - 2x + 2)x4+4=(x2+2)2−4x2=(x2+2x+2)(x2−2x+2) (2) a4−7a2+9=(a2−3)2−a2=(a2−a−3)(a2+a−3)a^4 - 7a^2 + 9 = (a^2 - 3)^2 - a^2 = (a^2 - a - 3)(a^2 + a - 3)a4−7a2+9=(a2−3)2−a2=(a2−a−3)(a2+a−3) (3) p4+p2+25=(p2+5)2−9p2=(p2+3p+5)(p2−3p+5)p^4 + p^2 + 25 = (p^2 + 5)^2 - 9p^2 = (p^2 + 3p + 5)(p^2 - 3p + 5)p4+p2+25=(p2+5)2−9p2=(p2+3p+5)(p2−3p+5) (4) p4−13p2q2+4q4=(p2−2q2)2−9p2q2=(p2+3pq−2q2)(p2−3pq−2q2)p^4 - 13p^2q^2 + 4q^4 = (p^2 - 2q^2)^2 - 9p^2q^2 = (p^2 + 3pq - 2q^2)(p^2 - 3pq - 2q^2)p4−13p2q2+4q4=(p2−2q2)2−9p2q2=(p2+3pq−2q2)(p2−3pq−2q2)