## Curry 4 years ago sigma

1. Curry

$\sum_{x=1}^{25}$ K^2 -3k +4 what is the formula to solve if u dont have calculator

2. Curry

3. anonymous

$\sum_{x=1}^{25}k^2-3\sum_{x=1}^{25}k+4\sum_{x=1}^{25}1$

4. anonymous

5. anonymous

but this one is pretty easy $4\sum_{k=1}^{25}1=4\times 25=100$

6. anonymous

sum 1 to n of (1) is equal to n sum 1 to n of (i) is equal to n(n+1)/2 sum 1 to n of (i^2) is equal to n(n+1)(2n+1)/6 um i think.

7. anonymous

yes, agreed^

8. anonymous

@curry you got this?

9. anonymous

$\sum_{k=1}^{n}k=\frac{n(n+1)}{2}$ so $-3\sum_{k=1}^{25}k=-3\times \frac{25\times 26}{2}$

10. Curry

kind a

11. anonymous

$\sum_{k=1}^nk^2=\frac{n(n+1)(2n+1)}{6}$ so $\sum_{k=1}^{25}k^2=\frac{25(26)(51)}{6}$

12. anonymous

now you have all the numbers you need, grind it out with a calculator

13. anonymous

should get 4650 if you do it right http://www.wolframalpha.com/input/?i=sum+k+%3D+1+to+25+%28k^2-3k%2B4%29