فيم يلى امتحان جبر(math-1)
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1) a) Graph the curve of the function then deduce the
range , monotony and its type


need graph

B) In an arithmetic sequence the sum of its first and third terms = 10
and its tenth term = 21, how many terms starting from the first
should be taken to make the sum = 440 ?



when s1 + s3 = 10
then
a + a+ 2r = 10
then
2a + 2 r = 10
then
a +r = 5
and
the tenth term = 21
then
a + 9 r = 21
subtract the two equ
then
8r = 16
then
r = 2
and
a = 3
thearithmetic sequence
is
( 3 ,5, 7 , ....................... )

the sum = 440 then
n / 2 ) ( 2 a + ( n - 1 ) r = 440
when
a= 3 and r = 2
then
n ( n + 2 ) = 440
n ( n + 2 ) = 22 * 20
then
n = 22
good lock for all

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