⑤a²-1/4b² ⑥(x-y)²/4 — (x+y)²/4 ⑦1/3x³-3x

⑤a²-1/4b² ⑥(x-y)²/4 — (x+y)²/4 ⑦1/3x³-3x
⑤a²-1/4b² ⑥(x-y)²/4 — (x+y)²/4 ⑦1/3x³-3x

⑤a²-1/4b² ⑥(x-y)²/4 — (x+y)²/4 ⑦1/3x³-3x
⑤a²-1/4b²
=1/4(4a²-b²)
=1/4(2a+b)(2a-b)
⑥(x-y)²/4 — (x+y)²/4
=1/4[(x-y)²-(x+y)²]
=1/4(x²-2xy+y²-x²-2xy-y²)
=-xy
⑦1/3x³-3x
=1/3x (x²-9）
=1/3x(x+3)(x-3)