Question

Which equation has the components of 0 = x2 – 9x – 20 inserted into the quadratic formula correctly? x = StartFraction negative 9 plus or minus StartRoot (negative 9) squared minus 4(1)(negative 20) EndRoot Over 2(1) EndFraction x = StartFraction 9 plus or minus StartRoot (negative 9) squared minus 4(1)(20) EndRoot Over 2(1) EndFraction x = StartFraction 9 plus or minus StartRoot (negative 9) squared minus 4(1)(negative 20) EndRoot Over 2(1) EndFraction x = StartFraction negative 9 plus or minus StartRoot (negative 9) squared + 4(1)(negative 20) EndRoot Over 2(1) EndFraction

Answer 1

Answer:

$x=\frac{9+/-\sqrt{(-9)^2-4\,(1)\,(-20)} }{2\,(1)}$

Step-by-step explanation:

Recall that the quadratic formula gives you the pattern to follow in order to find the solutions to a quadratic equation of the form: $ax^2+bx+c=0$

It tells us that we need to use the parameters $a,\, b,$ and $c$ in the following formula in order to get the answers for the x-values that solve it:

$x=\frac{-b+/-\sqrt{b^2-4\,a\,c} }{2\,a}$

so, in our case, $a=1$, $b=-9$, and $c=-20$

then, replacing these values in the formula, we obtain:

$x=\frac{-b+/-\sqrt{b^2-4\,a\,c} }{2\,a}\\x=\frac{-(-9)+/-\sqrt{(-9)^2-4\,(1)\,(-20)} }{2\,(1)}\\x=\frac{9+/-\sqrt{(-9)^2-4\,(1)\,(-20)} }{2\,(1)}$

Which looks like the third expression you are listing (although it is a little hard to read)

Answer 2

Answer: C

Step-by-step explanation: No cap