Найдите значение выражения: 51/4(12-c)+31/4(-c-8) при c=-0.4

Question

Найдите значение выражения: 51/4(12-c)+31/4(-c-8) при c=-0.4

Answer 1

51/4(12-(-0.4))+31/4(-(-0.4)-8)=

=51/4(12+0.4)+31/4(0.4-8)=

=51/4×12.4+31/4×(-7.6)=

=51/4×62/5+31/4×(-38/5)=

=51/2×31/5-31/2×19/5=

=1581/10-589/10=

=496/5=99,2