Question

а) (2a+5)(2a-5) при a = -1,5; 2,5;4.

Answer 1

4a² - 10a + 10a - 25 = 4a² - 25
При a = - 1,5 :
4a² - 25 = 4 × ( - 1,5)²  - 25 = 4 × 2,25 - 25 = 9 - 25 = - 16
При a = 2,5 :
4a² - 25 = 4 × 2,5² - 25 = 4 × 6,25 - 25= 25 - 25 = 0
При a = 4 :
4a² - 25 = 4 × 4² - 25 = 4 × 16 - 25 = 64 - 25 = 39