Question

{A+2d=15} x {2a+2d=25}. =?

Answer 1

$\huge\boxed{\fcolorbox{cyan}{blue}{Solution }}$

S10=10÷2 (2a +(10-1)d=5 (2a+9d)

125=5 (2a+9d)

125÷5=2a+9d

25=2a+9d _(1)

a3=a+2d

15=a+2d _(2)

subtracting equation (2) from (1) ,we get

2a+9d -a -2d =25-15

a+7d=10

a=10-7d _(3)

put the value of a in equation (2)

15=10-7d +2d

d=-1

put d=-1 in (3)

a=10-(-1×7)

a=17

now, a10=a+9d

a10=17-9

a10=8

Answer 2

Answer:

S10=10÷2 (2a +(10-1)d=5 (2a+9d)

125=5 (2a+9d)

125÷5=2a+9d

25=2a+9d _(1)

a3=a+2d

15=a+2d _(2)

subtracting equation (2) from (1) ,we get

2a+9d -a -2d =25-15

a+7d=10

a=10-7d _(3)

put the value of a in equation (2)

15=10-7d +2d

d=-1

put d=-1 in (3)

a=10-(-1×7)

a=17

now, a10=a+9d

a10=17-9

a10=8

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