Question

(2,5 a -1.5b)^2-(1.5a-2.5b)^2 если a=-1.5 b =3.5

Answer 1

(2,5a - 1,5b)² - (1,5a - 2,5b)² =

= 6,25а² - 7,5аb + 2,25b² - 2,25a² + 7,5ab - 6,25b² =

= 4a² - 4b² = 4(a + b)(a - b)

если a = -1,5 b = 3,5

4(a + b)(a - b) = 4 · (-1.5 + 3.5)(-1.5 - 3.5) = 4 · 2 · (-5) = -40

Answer 2

(2,5a-1,5b)²-(1,5a-2,5b)²=

(2,5a-1,5b-1,5a+2,5b)(2,5a-1,5b+1,5a-2,5b)

=(2,5(a+b)-1,5(a+b))(2,5(a-b)+1,5(a-b))=

4(a+b)(a-b)=4*2(-5)=-40