Verified answer

[tex]\displaysztyle\bf\\a=0,8\\\\b=0,6\\\\\\(2a-5b)^{2} -(2a+5b)^{2} =(2a-5b-2a-5b)\cdot(2a-5b+2a+5b)=\\\\=-10b\cdot 4a=-40\cdot a\cdot b\\\\\\-40\cdot a\cdot b=-40\cdot 0,8\cdot 0,6=-19,2[/tex]

Ответ:

(2×0,8-5×0,6)^2 -(2×0,8+5×0,6)^2=-19,2