Efectuoaţi:a) (x²-5)(x²+5)=
b) (4+y²)(4-y²)
c)(9a-v)(9a+b)
d)(0,7x+y²)(0,7x-y²)
(√2-1)(√2+1)
(√3+√2)(√3-√2)
(√5-√3)(√5+√3)
Vă rog urgent !