Answer:
C= 30
Step-by-step explanation:
option D is the answer.!!!!
three hundred thousand twenty-one two hundred nine
-x^2+105x-1050=1550
We move all terms to the left:
-x^2+105x-1050-(1550)=0
We add all the numbers together, and all the variables
-1x^2+105x-2600=0
a = -1; b = 105; c = -2600;
Δ = b2-4ac
Δ = 1052-4·(-1)·(-2600)
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
<span><span>x1</span>=<span><span>−b−<span>Δ√</span></span><span>2a</span></span></span><span><span>x2</span>=<span><span>−b+<span>Δ√</span></span><span>2a</span></span></span>
<span><span>Δ<span>−−</span>√</span>=<span>625<span>−−−</span>√</span>=25</span>
<span><span>x1</span>=<span><span>−b−<span>Δ√</span></span><span>2a</span></span>=<span><span>−(105)−25</span><span>2∗−1</span></span>=<span><span>−130</span><span>−2</span></span>=+65</span>
<span><span><span>x2</span>=<span><span>−b+<span>Δ√</span></span><span>2a</span></span>=<span><span>−(105)+25</span><span>2∗−1</span></span>=<span><span>−80</span><span>−2</span></span>=+40</span></span>
