Answer:
the least common multiple is 18
Step-by-step explanation:
Answer:
S₁₅ = 645
Step-by-step explanation:
The sum to n terms of an arithmetic sequence is
=
[ 2a₁ + (n - 1)d ]
where a₁ is the first term and d the common difference
Using the nth term formula
= 5n + 3 , then
a₁ = 5(1) + 3 = 5 + 3 = 8
a₂ = 5(2) + 3 = 10 + 3 = 13 , then
d = a₂ - a₁ = 13 - 8 = 5
Thus
S₁₅ =
[ (2 × 8) + (14 × 5) ]
= 7.5( 16 + 70)
= 7.5 × 86
= 645
It is given in the question that
BD is the median. So it divides the opposite sides in two equal parts .
Therefore in triangles BAD and BCD,
AB and AC are congruent because of isosceles triangle.
AD and CD are congruent because of the median BD.
And BD and BD are congruent .
So the two triangles are congruent by SSS and the correct option is the first option .