1.8903
because if you do the math its easy
Answer:

Step-by-step explanation:


Answer:
t12= -8
Step-by-step explanation:
t3
a+2d=10 (1)
t10
a+9d=-4. (2)
From (1)
a=10-2d. (3)
Sub into (3) into equ (2)
a+9d=-4
10-2d+9d=-4
10+7d=-4
7d=-4-10
7d=-14
Divide both sides by 7
d=-14/7
d= -2
10=a+2d
10=a+2(-2)
10=a-4
10+4=a
14=a
a=14
t12=a+11d
= 14+11(-2)
=14-22
= -8
t12= -8
<h3>To ProvE :- </h3>
- 1 + 3 + 5 + ..... + (2n - 1) = n²
<u>Method</u><u> </u><u>:</u><u>-</u>
If P(n) is a statement such that ,
- P(n) is true for n = 1
- P(n) is true for n = k + 1 , when it's true for n = k ( k is a natural number ) , then the statement is true for all natural numbers .
Step 1 : <u>Put </u><u>n </u><u>=</u><u> </u><u>1</u><u> </u><u>:</u><u>-</u><u> </u>
Step 2 : <u>Assume </u><u>that </u><u>P(</u><u>n)</u><u> </u><u>is </u><u>true </u><u>for </u><u>n </u><u>=</u><u> </u><u>k </u><u>:</u><u>-</u>

- Add (2k +1) to both sides .
- RHS is in the form of ( a + b)² = a²+b²+2ab .
- Adding and subtracting 1 to LHS .
- P(n) is true for n = k + 1 .
Hence by the principal of Mathematical Induction we can say that P(n) is true for all natural numbers 'n' .
<em>*</em><em>*</em><em>Edits</em><em> are</em><em> welcomed</em><em>*</em><em>*</em>