Step-by-step explanation:
Explanation:
Given:
−3x2+12x+1=0
This is in the form:
ax2+bx+c=0
with a=−3, b=12 and c=1
In order to decide which method to use, we can first examine the discriminant:
Δ=b2−4ac=122−4(−3)(1)=144+12=156
Since Δ>0 we can tell that the quadratic has 2 distinct real solutions, but because it is not a perfect square we can also tell that those solutions are irrational.
So there is no rational factorisation and we can discount the use of an AC method or similar.
We can use the quadratic formula or we can complete the square.
If we choose to use the quadratic formula, then we find:
x=−b±√b2−4ac2a
x=−b±√Δ2a
x=−(12)±√1562(−3)
x=−12±2√39−6
x=2±√393
When completing the square, note that b=12 is already divisible by a=−3 and by
A. down
The -4 moves the y-intercept down from the origin to -4
Add the sales tax to the bill:
Bill with tax = 14.60 x 1.09 = $15.95
Multiply the total bill by the tip percentage:
Tip = 15.95 x 0.19 = 3.02
Tip = $3.02
