the general form of an arthimetic progression is a, a+d,a+2d........but in the given picture how did we get a-d. 7th question
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swathika23:
thats why we have a-d
yeah thanks !
: )
hooooi
tnks
its ok!
even i had the same doubt then cleared
i also explained the same thing ! pls refer my answer . i was the one to answer first .. plss refer
yes
the answer given in the 7th question above is wrong.
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Answered by
2
There is something wrong in the answer given there.... It says to find the ratio of sides. It did not say that the ratios are equal. final step saying that a^2 - d^2 = a^2 is TOTALLY WRONG.
Normally we have an AP as a, a+d, a+2d.. Sometimes for ease of calculations, we start the first term as a-d.. The calculation steps are more cumbersome if we use a, a+d, a+2d.
Proper answer to qn 7:
Let a-d , a, a+d be the sides of a right angled triangle. a+d is the largest and the hypotenuse.
(a-d)² + a² = (a+d)²
a² + d² - 2 a d + a² = a² + d² + 2 a d
a² = 4 a d
a = 4 d
So the sides are : 3d, 4d, 5d.
Their ratios: 3 : 4 : 5
Because we used a, a+d, a+2d, the terms on LHS and RHS of Pythagoras theorem do not cancel out. So the answer cannot be arrived at easily.
Normally we have an AP as a, a+d, a+2d.. Sometimes for ease of calculations, we start the first term as a-d.. The calculation steps are more cumbersome if we use a, a+d, a+2d.
Proper answer to qn 7:
Let a-d , a, a+d be the sides of a right angled triangle. a+d is the largest and the hypotenuse.
(a-d)² + a² = (a+d)²
a² + d² - 2 a d + a² = a² + d² + 2 a d
a² = 4 a d
a = 4 d
So the sides are : 3d, 4d, 5d.
Their ratios: 3 : 4 : 5
Because we used a, a+d, a+2d, the terms on LHS and RHS of Pythagoras theorem do not cancel out. So the answer cannot be arrived at easily.
click on red heart thanks above pls
Answered by
0
Hi friend there is nothing wrong in the answer.....
it's is correct that general term of A.P is
a , a+d, a+2d ......so on..
but there are some cases which you should have to remember ...
if there are three term you have to assume it such a way that when we add all term common difference get cancel out...like in question sided of triangle are three so you have to assume three terms of A.P. as a-d, a , a+d
on adding u see that common difference got cancel ..it is assume to simplify problem ....
so u should remember...
1) if three term is required assume as
a-d , a , a+d
2) if four terms are required then assume as
a-2d , a-d , a+d , a+2d
I hope it will help you ....
it's is correct that general term of A.P is
a , a+d, a+2d ......so on..
but there are some cases which you should have to remember ...
if there are three term you have to assume it such a way that when we add all term common difference get cancel out...like in question sided of triangle are three so you have to assume three terms of A.P. as a-d, a , a+d
on adding u see that common difference got cancel ..it is assume to simplify problem ....
so u should remember...
1) if three term is required assume as
a-d , a , a+d
2) if four terms are required then assume as
a-2d , a-d , a+d , a+2d
I hope it will help you ....
but the solution was wrong...
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