Answer:
10.6
x
+
26.5
Step-by-step explanation:
Answer:
no thanks
Step-by-step explanation:
Answer:
Step-by-step explanation:
This is the SUM of two PRODUCTS.
Answer:
Sum of it's 15 terms is -15
Step-by-step explanation:
S6=n/2{2a+(n-1)d}
9=6/2{2a+(6-1)d}
9=3{2a+(5)d}
9=3{2a+5d}
9=6a+15d
6=9/2{2a+(n-1)d}
6=4.5{2a+(9-1)d}
6=4.5{2a+(8)d}
6=4.5(2a+8d)
6=9a+36d
6a+15d=9 (1)
9a+36d=6 (2)
Multiply (1) by 6 and (2) by 4
36a+90d=54
36a+144d=24
Subtract (2) from (1)
-54d=30
d=30/-54
d=-10/18
=-5/9
9a+36d=6
9a+36(-5/9)=6
9a-180/9=6
9a-20=6
9a=6+20
9a=26
a=26/9
Check
6a+15d=9
6(26/9)+15(-5/9)
=156/9-75/9
=17.33-8.33
=9
Sum of it's 15 terms=n/2{2a+(n-1)d}
=15/2{2(26/9) + (15-1)-5/9}
=7.5{52/9 + (14)-5/9}
=7.5{52/9 -70/9}
=390/9-525/9
=390-525/9
=-135/9
=-15
Sum of it's 15 terms is -15
