hello :
false because : Y^4 = 16 ... Y^4 -16 =0
(y²)²-4² =0..... (1)
bu identity : a²-b² =(a+b)(a-b
(1) equi : (y²-4)(y²+4) =0
but : y²-4 =y²-2² = (y+2)(y-2) = 0
y+2=0 or y-2=0
y=2 or y = -2
y²+4 =0...... y²=-4 no solution in R
conclusion 2 solutions : -2 and 2
