Example If x = 4 and y = 3 find the
value of
Solution:
Example If a = 2, b = 3, c = 2 evaluate
2 a + 3 b + 4 c.
Solution: 2 a + 3 b + 4 c = 2 ( 2 ) + 3 ( 3 ) + 4
( 2 )
= 4 + 9 + 8
= 21
Example Evaluate 2 a^{2} + 5 b + 7 if a = 2, and b = 1
Solution: 2 a^{2} + 5 b + 7 =
2 ( 2 )^{2} + 5 ( 1 ) + 7
= 2 ( 4 ) + 5 + 7
=
8 + 12
= 20
Example Tom and Jackson walk at a rate of
x and y km / hr respectively. If they start from the same spot and
go in the same direction, what is the distance between them after
t hours ( y > x ). Calculate the distance if x = 3, y = 4 and
t = 2.
Solution: In ‘ t ’ hours Tom will reach
the distance of xt km
(\ distance = speed ´
time ). In ‘ t ’ hours Jackson will reach the distance of y t km.
Since y > x and t > 0 we have y t > x t . \
y t  x t = distance between Tom and Jackson after ‘ t ’ hours.
( Note that they walk in the same direction
Þ both x and y are positive ).
Taking x = 3, y = 4 and t = 2 in y t  x t we get, (4) (2)  (3) (2) = 8  6 = 2 km.
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