Нужно знать формулу разности квадратов: a² - b² = (a - b)(a + b).
Поэтому:
1) (x - 2)² - 4 = (х - 2)² - 2² = (х - 2 - 2)(х - 2 + 2) = (х - 4)х;
2) (b + 7)² - 100с² = (b + 7)² - (10с)² = (b + 7 - 10с)(b + 7 + 10с);
3) 121 - (b + 7)² = 11² - (b + 7)² = (11 - (b + 7))(11 + (b + 7)) = (11 - b - 7)(11 + b + 7) =
= (4 - b)(18 + b).
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Verified answer
Нужно знать формулу разности квадратов: a² - b² = (a - b)(a + b).
Поэтому:
1) (x - 2)² - 4 = (х - 2)² - 2² = (х - 2 - 2)(х - 2 + 2) = (х - 4)х;
2) (b + 7)² - 100с² = (b + 7)² - (10с)² = (b + 7 - 10с)(b + 7 + 10с);
3) 121 - (b + 7)² = 11² - (b + 7)² = (11 - (b + 7))(11 + (b + 7)) = (11 - b - 7)(11 + b + 7) =
= (4 - b)(18 + b).