Answer:
The correct option is D.
Step-by-step explanation:
a = 9c²+4
b= 7+3c
Firstly solve 2nd equation for c in terms of b:
b=7+3c
b-7=3c
b-7/3 = c
Now substitute the value of c in equation 1:
a= 9c²+4
a=9(b-7/3)² +4
a=9(b-7)²/9+4
9 will be cancelled by 9, so the equation we get is:
a=(b-7)²+4
Apply whole square formula for (b-7)²
a=b²-14b+49+4
Solve like terms:
a=b²-14b+53
Therefore the correct option is D....
