Question

49a²+4b²+7a+2b+28ab-12,если 3,5a+b=2,5
срочно ​

Answer 1

49a²+4b²+7a+2b+28ab-12 = 49a²+28ab4b²+7a+2b-12 = (7a+2b)²+7a+2b-12.

3,5a+b=2,5 | * 2

7a + 2b = 5

(7a+2b)²+7a+2b-12 = 5² + 5 - 12 = 25 + 5 - 12 = 18

Answer 2

$\displaystyle\bf\\3,5a+b=2,5 \ \ \ \Rightarrow \ \ \ 7a+2b=5\\\\49a^{2} +4b^{2} +7a+2b+28ab-12=\Big(49a^{2} +28ab+4b^{2} \Big)+\Big(7a+2b\Big)-12=\\\\\\=\Big(\underbrace{7a+2b}_{5}\Big)^{2} +\Big(\underbrace{7a+2b}_{5}\Big)-12=5^{2} +5-12=25-7=18\\\\\\Otvet \ : \ 18$