If m times the mth term of an A.P is equal to n times its nth term, show that the (m+n)th term of the A.P is zero.
Given :--
m{a +(m-1)d} = n{a +(n-1)d}
ma + m2d -md = na +n2d -nd
ma - na + m2d - n2d -md +nd = 0
a(m-n) +d(m2 - n2) -d(m-n) = 0
(m-n) (a + d(m+n) -d) = 0
(a + d(m+n) -d) = 0
a + (m+n - 1)d = 0
thus, (m+n)th term = 0....proved..
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Let mth term be am and nth term be an
According to the question :
m(am ) = n(an )
Apply Formula : an = a + (n-1) *d [ a - first term , d -Common Difference , n - No of terms ]
m( a + (m-1) *d ) = n( a + (n-1) *d )
{ma + (m2 - m) d }= [na + (n2 - n) d]
{ma + (m2 d- md) }= [na + (n2 d- nd) ]
[ma-na] + { m2 d- n2 d } + (nd-md) = 0
a*[m-n] + d* { m2 - n2 } + d* (n-m) = 0
Apply : a2 - b2 = (a+b) (a-b)
a*[m-n] + d* { (m+n) (m-n) } - d* (m - n) = 0
Divide the above equation with " (m-n)" ,We get :
a + d* { (m+n) } - d = 0
a + { (m+n) - 1 } d = 0
COMPARING THE EQUATION WITH : an = a + (n-1) *d
Therefore : a + { (m+n) - 1 } d = am+n
So : am+n = 0
So :the (m+n)th term of the A.P is zero
(HENCE PROVED)
If you are satisfied do give thumbs up.
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Given m × tm = n × tn
⇒ m[a + (m – 1)d] = n[a + (n – 1)d]
⇒ ma + m(m – 1)d] = na + n(n – 1)d
⇒ ma + m(m – 1)d] – na – n(n – 1)d = 0
⇒ a(m – n) + [m2 – m – n2 + n]d = 0
⇒ a(m – n) + [m2 – n2 – m + n]d = 0
⇒ a(m – n) + [(m – n)(m + n) – (m – n)]d = 0
⇒ (m – n)[a+ {(m + n) – 1}]d = 0
⇒ [a+ {(m + n) – 1}]d = 0
Hence t(m + n) = 0
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Given m × tm = n × tn
⇒ m[a + (m – 1)d] = n[a + (n – 1)d]
⇒ ma + m(m – 1)d] = na + n(n – 1)d
⇒ ma + m(m – 1)d] – na – n(n – 1)d = 0
⇒ a(m – n) + [m2 – m – n2 + n]d = 0
⇒ a(m – n) + [m2 – n2 – m + n]d = 0
⇒ a(m – n) + [(m – n)(m + n) – (m – n)]d = 0
⇒ (m – n)[a+ {(m + n) – 1}]d = 0
⇒ [a+ {(m + n) – 1}]d = 0
Hence t(m + n) = 0
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⇒ m[a + (m – 1)d] = n[a + (n – 1)d]
⇒ ma + m(m – 1)d] = na + n(n – 1)d
⇒ ma + m(m – 1)d] – na – n(n – 1)d = 0
⇒ a(m – n) + [m2 – m – n2 + n]d = 0
⇒ a(m – n) + [m2 – n2 – m + n]d = 0
⇒ a(m – n) + [(m – n)(m + n) – (m – n)]d = 0
⇒ (m – n)[a+ {(m + n) – 1}]d = 0
⇒ [a+ {(m + n) – 1}]d = 0
Hence t(m + n) = 0
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ii) So mth term is: {a + (m - 1)d} and nth term is [a + (n - 1)d}
iii) As given, m{a + (m - 1) d} = n{a + (n - 1)d}
Expanding, rearranging and simplifying,
(m - n)a + (m² - n²)d - (m - n)d = 0
Factorizing, (m - n)*[a + {(m + n) - 1}d] = 0 ---- (1)
Since m & n are different the factor (m - n) is not equal to zero.
Hence equation (1) = 0, implies that [a + {(m + n) - 1}d] = 0
But this (m + n)th term of the AP.
Thus it is proved that (m + n)th term of this AP = 0
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- -3
m(a ) = n(a ) Apply Formula : a = a + (n-1) *d [ a - rst term , d -Common Difference , n - No of terms ]
m( a + (m-1) *d ) = n( a + (n-1) *d ) {ma + (m - m) d }= [na + (n - n) d] {ma + (m d- md) }= [na + (n d- nd) ] [ma-na] + { m d- n d } + (nd-md) = 0 a*[m-n] + d* { m - n } + d* (n-m) = 0 Apply : a - b = (a+b) (a-b) a*[m-n] + d* { (m+n) (m-n) } - d* (m - n) = 0 Divide the above equation with " (m-n)" ,We get : a + d* { (m+n) } - d = 0 a + { (m+n) - 1 } d = 0 COMPARING THE EQUATION WITH : a = a + (n-1) *d Therefore : a + { (m+n) - 1 } d = a So : a = 0 So :the (m+n)th term of the A.P is zero (HENCE PROVED) If you are satised do give thumbs up
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nth term = a + (n-1) d
Given that m{a +(m-1)d} = n{a + (n -1)d}
⇒ am + m²d -md = an + n²d - nd
⇒ am - an + m²d - n²d -md + nd = 0
⇒ a(m-n) + (m²-n²)d - (m-n)d = 0
⇒ a(m-n) + {(m-n)(m+n)}d -(m-n)d = 0
⇒ a(m-n) + {(m-n)(m+n) - (m-n)} d = 0
⇒ a(m-n) + (m-n)(m+n -1) d = 0
⇒ (m-n){a + (m+n-1)d} = 0
⇒ a + (m+n -1)d = 0/(m-n)
⇒ a + (m+n -1)d = 0
hence proved :)
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