Given that g(x)=2x'2 +7x and g(a) = 30 then
30 = 2a^2 + 7a
2a^2 + 7a - 30 = 0
2a^2 + 12a - 5a - 30 = 0
factorizing
2a(a + 6) -5(a + 6) = 0
(2a - 5)(a + 6) = 0
2a - 5 = 0 or a + 6 = 0
2a = 5 or a = -6
a = 5/2 or -6
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