+2498 \(2(a^2-25)=21a\\ a^2-25=10.5a\\ a^2-10.5a-25=0\)
Do the rest by yourself then write the answer
+776 2(a-5)(a+5)=21a
solve for a.
just so i won't cunfuse you:
2(a-5)(a+5)=(2a-10)(a-5)
that means:
(2a-10)(a-5)=
2a²-10a-10a-50=
2a²-20a-50=
21a
divide both sides by a:
2a-10-(50/a)=21
add 10:
2a-(50/a)=31
divide by two:
a-(25/a)=15.5
multiply by a:
a²-25=15.5/a
subtract 25 and take the square root:
a=sqrt((15.5/a)-25)
idk how to get the rest, but, at least it might help.
+194 the corrrect answer would be a=10.5
as 2(a)=21 in that expression a equals 10.5
