Question

a^2-b^2=45 si a+b=15 atunci 5a-5b este:
A.5; B.15; C.3; D.0
Dau coroana, urgent!!

Answer 1

a+b=15 => a=15-b
(15-b)^2-b^2=45
225-30b+b^2-b^2=45
225-30b=45
180=30b
b=6

a+6=15
a=9

5a-5b=
5*9-5*6=
45-30=15