The equation 2x2−23x+c=0 has roots p and 2p.
Using Vieta's formulas (relationships between roots and coefficients):
| Relationship | Formula | Substitution |
|---|
| Sum of roots | p+2p=23/2 | 3p=23 |
| Product of roots | p⋅2p=2c | 2p2=2c |
From the sum: 3p=23 gives us p=21
From the product: 2p2=2c
Substituting p=21:
2⋅(21)2=2c
2⋅41=2c
21=2c
c=22=21
Now we calculate 64(p6+c12):
p6=(21)6=641
c12=(21)12=(2)121=(21/2)121=261=641
Therefore: 64(p6+c12)=64(641+641)=64⋅642=2
So one root of the equation a2x2+12a−7=0 is x=2.
Substituting x=2 into the equation:
a2(2)2+12a−7=0
4a2+12a−7=0
Using the quadratic formula where A=4, B=12, C=−7:
a=8−12±144+112=8−12±256=8−12±16
This gives: a=84=21 or a=8−28=−27
Since a>0, we have a=21
Answer: Option 2