SOLUTION: 1.The 4th and 6th term of an A.P is 6 and 24 respectively. Find (1) the sum of the first seven term (ii) the eight term
2.solve the following quadratically (1)x square-5x-6
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-> SOLUTION: 1.The 4th and 6th term of an A.P is 6 and 24 respectively. Find (1) the sum of the first seven term (ii) the eight term
2.solve the following quadratically (1)x square-5x-6
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Question 1098950: 1.The 4th and 6th term of an A.P is 6 and 24 respectively. Find (1) the sum of the first seven term (ii) the eight term
2.solve the following quadratically (1)x square-5x-6 Answer by ikleyn(52832) (Show Source):
Between the 6th and 4th terms of an AP there is the room for two common differencies;
therefore, the common difference d = = = 9.
In more formal way, = - = 2d = 24 - 6 = 18, hence, d = = 9.
Then = = 6 - 3*9 = -21.
As you know now and d, you actually know EVERYTHING about the given AP.
For example, = = -21 + 6*9 = 33.
Now, the sum of the first 7 terms is = = = 42.
= = -21+ 7*9 = 42.
