FUNCTIONS 6

If F(x) = 4x² + 12x - 420; find F(10) - F(2).

solution

PROCEDURE:

i) Find F(10)

ii) Find F(2)

iii) Do F(10) - F(2).

i) Find F(10)

F(x) = 4x² + 12x - 420

F(10) = 4(10)² + 12(10) - 420

F(10) = 4(10 x 10) + (12 x 10) - 420

F(10) = 400 + 120 - 420

F(10) = 520 - 420

F(10) = 100.

ii) Find F(2)

F(x) = 4x² + 12x - 420

F(2) = 4(2)² + 12(2) - 420

F(5) = 4(2 x 2) + (12 x 2) - 420

F(5) = 32 + 24 - 420

F(5) = 56 - 420

F(5) = -364

iii) Do F(10) - F(5).

      F(10) - F(5) = 100 - (-364) = 100 + 364 = 464.

Hence F(10) - F(5) = 464.

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

If F(x) = 5x² + 7x - 10; find F(10) - F(4).