The ratio of sum of m and n terms of an AP is m sq. :n sq. show that r...
Explanation:
Given:
Sum of m and n terms of an AP= m sq. :n sq.
To prove:
Ratio of mth and nth term is m/n=2m-1/2n-1
Formula:
Sum of first n terms of an AP= n/2[2a+(n-1)d]
Sum of first m terms of an AP= m/2[2a+(m-1)d]
mth term of an AP= a+(m-1)d
nth term of an AP= a+(n-1)d
Proof:
Given, Sum of m and n terms of an AP= m sq. :n sq.
So, m/2[2a+(m-1)d] : n/2[2a+(n-1)d] = m sq. :n sq.
On simplifying, we get,
(2a+(m-1)d)/(2a+(n-1)d) = m/n
On cross multiplying, we get,
mn(2a+(m-1)d)=nm(2a+(n-1)d)
On solving, we get,
md+nd-m-n=0
d(m+n)=m-n
d=(m-n)/(m+n)
Now, we can find the mth and nth term of the AP.
mth term of an AP= a+(m-1)d
Substituting the value of d, we get,
mth term of an AP = a + (m-1)(m-n)/(m+n)
nth term of an AP= a+(n-1)d
Substituting the value of d, we get,
nth term of an AP = a + (n-1)(m-n)/(m+n)
Now, we can find the ratio of mth and nth term.
Ratio of mth and nth term = (a + (m-1)(m-n)/(m+n))/(a + (n-1)(m-n)/(m+n))
On simplifying, we get,
Ratio of mth and nth term = m/n=2m-1/2n-1
Conclusion:
Hence, the ratio of mth and nth term is m/n=2m-1/2n-1