FUNCTIONS-5

If F(x) = 4x² + 12x - 420; find F(6) - F(4).

solution

PROCEDURE:

i) Find F(6)

ii) Find F(4)

iii) Do F(6) - F(4).

i) Find F(6)

F(x) = 4x² + 12x - 420

F(6) = 4(6)² + 12(6) - 420

F(6) = 4(6x 6) + (12 x 6) - 420

F(6) = 144 + 72 - 420

F(6) = 216 - 420

F(6) = -204.

ii) Find F(2)

F(x) = 4x² + 12x - 420

F(4) = 4(4)² + 12(4) - 420

F(4) = 4(4 x 4) + (12 x 4) - 420

F(4) = 64 + 48 - 420

F(4) = 112 - 420

F(4) = -308

iii) Do F(4) - F(2).

      F(6) - F(4) = -204 - (-308) = -204 + 308 = 104.

Hence F(4) - F(2) = 104.

TRY THIS..................

If F(x) = 15x² + 2x - 3; find F(8) - F(3).