` 3) ` ` 121 - (x - 2)^2 `
` = 11^2 - (x - 2)^2 `
` = (11 - x + 2)(11 + x - 2) `
` = (13 - x)(x + 9) `
` 4) ` ` 81 - (5 - y)^2 `
` = 9^2 - (5 - y)^2 `
` = (9 - 5 + y)(9 + 5 - y) `
` = (4 + y)(14 - y) `
` 5) ` ` (x - 6)^2 - 64 `
` = (x - 6)^2 - 8^2 `
` = (x - 6 - 8)(x - 6 + 8) `
` = (x - 14)(x + 2) `
Khác:
` (a + 2)^2 - (b + 3)^2 `
` = (a + 2 - b - 3)(a + 2 + b + 3) `
` = (a - b - 1)(a + b + 5) `
` (a - 3)^2 - (b + 5)^2 `
` = (a - 3 - b - 5)(a - 3 + b + 5) `
` = (a - b - 8)(a + b + 2) `
` (a - 5)^2 - (b - 2)^2 `
` = (a - 5 - b + 2)(a - 5 + b - 2) `
` = (a - b - 3)(a + b - 7) `
