nomer 5. gimana tuh caranya

3 +7x -ax^2 = 0
ax^2 - 7x -3 = 0
x1 + x2 = -(-7)/a
-1/3 + x2 = 7/a
a = 7 / (-1/3+x2)

x1 x2 = -3/a
-1/3 x2 = -3/a
a = -3/ (-1/3x2)

7/(-1/3+x2) = -3/(-1/3x2)
-7/3 x2 = 1 -3x2
-7/3 x2 + 3x2 = 1
2/3 x2 = 1
x2 = 3/2

a= -3/(-1/3 x 3/2)
a = -3 / (-1/2)
a = 6 (Jawaban A)