This my few questions if u know pls help me & thank you!
1) Find tn of the A.P 4,9,14,...
2) The 7™ term of an A.P. is 32 and 13™ term is 62.find the A.P
3) The sum of the three consecutive number in A.P is 21 and their product is 231.find the number.
4) The sum of the first 'n' terms of an A.P is 3n²+5n.find the A.P.,hence find its 16™ term.
5)Find the root of the quadratic equation x²-9=0.
6)Solve 4x²-16+15=0 by completing square method.

2

Answers

2015-01-04T00:47:39+05:30

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1. a= 4 , d= 5 then tn = a + (n-1)d = 4 + (n-1) 5 = 5n-1 answer 2. t7 = a + (7-1) d => a+ 6d = 32 Now t13 = a+ (13-1)d => a+ 12d = 62 solve the equations and get the answer
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Yes but post them one by one
3) let the nos be ( x-d) , x , ( x+d) now according to question ( x-d) + x+ (x+d) = 21 => 3x = 21 => x=7 now multiplying ( 7 -d) x 7 x (7+d) = 231 => 49 -d^2 = 231/7 now solve it for d
Plz mark as best
But I not have that much points :-( ! So I post its all in ones! Thnx fr ur help..can you be my friend at fb? It will help me to ask u more problem,If you want^^
My answer coming d²=-16 => -4
2015-01-04T01:57:20+05:30

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Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
1) 
a=4,d=5\\\\T_n=a+(n-1)d=4+(n-1)5=5n-1\\\\2)\\a+6d=32,\ \ a+12d=62 \\difference=30=6d=>d=5 \\hence,\ a=2\\\\3)\\ numbers\ are=a-d,a,a+d\\\\sum=3a=21,\ a=7\\product=7(7^2-d^2)=231=7*33\\d=root(16)=4\\\\

4)
S_1 = 3*1^2+5*1= 8\\S_2=3*2^2+5*2=22\\\\T1= S_1 = 8\\d = S_2-S1= 14\\\\series =  8, 22, 36 .. = \\\\T_n = 8 + (n-1)14\\

5)
x^2 - 9 = 0\\\\x^2 = 9 = 3^2\\\\x = +root(9)  or  - root(9)\\\\x = +3  or  - 3\\\\

6)
is the given expression  4 x^2 - 16 + 15 ?  that is 4 x^2 - 1 = 0 ?
   then  x^2 = 1/4 
        x = +1/2   or  -1/2

or is  it    4 x^2 - 16 x + 15 = 0 ?          add and subtract  16 or 4^2
if so    (2x - 4)^2 - 16 + 15 = 0 
              2 x - 4 = + 1 or  -1 
                x =  5/2  or  3/2

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create questions and send their links on my profile. i will do tomorrow. good night.
I in 10th class :-) ! Yes its homework...
Good night SD thanks again^^ ,but how I send link on your profile. & I post many question in ones as I not have points :-( !if you at fb I will send you their!
write questions on my private messages or profile page. if there is no diagram.. make questions clearly..
OK! :-)