(2а+5)(2а-5) при а=-1.5; 2.5; 4​

(2а+5)(2а-5)=4a²-25

4a²-25= 4 * (-1,5)² - 25 = 4 * 2,25 - 25 = 9 - 25 = - 16

4a²-25= 4 * (2,5)² - 25 = 4 * 6,25 - 25 = 25 - 25 = 0

4a²-25= 4 * 4² - 25 = 4 * 16 - 25 = 64 - 25 = 39