b1(q^4-1)/(q-1)=15/2
b1/(q-1)=8
b1=8(1-q)
2b1(q^4-1)=15(q-1)
16(1-q)(q^4-1)=15(q-1)
1-q^4=15/16
q^4=1-15/16=1/16
q=1/2
b1=8*(1-q)=8*1/2=4
1)(c-0.5)*(c+0.5)
2)(x-4)^2
3)(2a-10)(4a^2+20a+100)
-16h(-3ik-6jk)-72hij=-48hik+96hjk-72hij=24(-2hik+4hjk-3hij)=
=24h(-2ik+4jk-3ij)