arithmetic progression?

1.) find the number of terms in the given Arithmethic Progression

-3,-11,-19,-27,…..,-115

2.)Three terms are in Arithmetic progression. If their sum is 21 and the sum of their squares is 149, what are the numbers?

3.) find S(sub)15 in Arithmethic progression 1,-7, -15,…,-111

hope you could help me with these…

I need your answers to verify my answers..I ll also try solving these…pls include ur solution!

that would be greatly appreciated!

Top 2 Answers

A few days ago

Anonymous

Favorite Answer

1) use the formula Tn = a+(n-1)*d

-115 = -3 + (n-1)*(-7)

2) let the three terms be a-d,a,a+d

then, 3a = 21, a = 7

the 3 terms are 7-d,7,7+d

(7-d)^2+49+(7+d)^2=149 …solve for d. Then you can get the 3 terms

3) Use Sn = n/2{a+l} Find n first using formula in (1)

A few days ago

lbelfer

I DID LEARN THIS LONG TIME EGO it should be formula for Arithmetihik Progression but what I remember it should be number that you add to each and to find: minus ferst from second or second from therd -11-(-3)=-11+3=-8 chek: -11+(-8)=-19 -19+(-8)=-27 -27+(-8)=-35 -35+(-8)=-43 -43+(-8)=-51 -51+(-8)=-59 but I forgot formula 2.) z+z+m+z+2m=21 and z*+(z+m)*+(z+2m)*=149 I GO SLEEP UFTER NIGHT SHIFT

Expand this: -3(x+2)(x-4)(x-2)(x+6)?

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