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Mathematics 8 Online
OpenStudy (diana.xl):

help?

OpenStudy (diana.xl):

Find the value of the discriminant for each quadratic equation below. Show all steps needed to write the answer in simplest form, including substituting the values of a, b, and c in the discriminant formula. Then use the value to determine how many real number solutions each equation has. 5x^2 + x = 4

OpenStudy (misty1212):

HI!!

OpenStudy (diana.xl):

Hey :)

OpenStudy (misty1212):

start by setting it equal to zero go from \[5x^2 + x = 4\] to \[5x^2+x-4=0\]

OpenStudy (misty1212):

\[\large \color{red}ax^2+\color{blue}bx+\color{green}c=0\] \[\huge \color{red}5x^2+\color{blue}1x+\color{green}{-4}=0\]

OpenStudy (misty1212):

then as @risn said compute \[\huge \color{blue}b^2-4\times \color{red}a\times \color{green}c\]

OpenStudy (diana.xl):

D= 1 - 4 (1)(-4)?

OpenStudy (misty1212):

nope

OpenStudy (misty1212):

\(\color{red}a=\color{red}{5}\)

OpenStudy (diana.xl):

oh sorry. D = 1-4(5)(-4)

OpenStudy (misty1212):

yeah that is right what do you get?

OpenStudy (diana.xl):

81?

OpenStudy (diana.xl):

as my final answer?

OpenStudy (misty1212):

yeah me too

OpenStudy (diana.xl):

at the end of the question it asks us "Then use the value to determine how many real number solutions each equation has".

OpenStudy (misty1212):

that is the answer to Show all steps needed to write the answer in simplest form, including substituting the values of a, b, and c in the discriminant formula.

OpenStudy (misty1212):

ok two steps here 81 is positive, so there are two real solutions also 81 is a "perfect square" it is the square of 9 that means both solutions are rational numbers

OpenStudy (diana.xl):

oh ok! thank u so much! :)

OpenStudy (misty1212):

in fact that means \[5x^2+x-4=0\] can be solved by factoring you get \[(5x-4)(x+1)=0\] so \[x=\frac{4}{5}\] or \[x=-1\]

OpenStudy (misty1212):

\[\color\magenta\heartsuit\]

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