If a + b = 1 and a - b = 7, then the value of 5(a2 + b2) is
25
35
50
125
2(a2 + b2) = (a + b)2 + (a - b)2 = 12 + 72 = 50 a2 + b2 = 25 5(a2 + b2) = 125