FUNCTIONS 8

If F(x) = 4x² + 12x - 100; find F(10) - F(5).

solution

PROCEDURE:

i) Find F(10)

ii) Find F(5)

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

i) Find F(10)

F(x) = 4x² + 12x - 100

F(10) = 4(10)² + 12(10) - 100

F(10) = 4(10 x 10) + (12 x 10) - 100

F(10) = 400 + 120 - 100

F(10) = 520 - 100

F(10) = 420.

ii) Find F(5)

F(x) = 4x² + 12x - 100

F(5) = 4(5)² + 12(5) - 100

F(5) = 4(5 x 5) + (12 x 5) - 100

F(5) = 100 + 60 - 100

F(5) = 160 - 100

F(5) = 60

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

      F(10) - F(5) = 420 - 60 = 360.

Hence F(10) - F(5) = 360.

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

If F(x) = 5x² + 7x - 200; find F(9) - F(3).