Question

Which are the solutions of x2 = –5x + 8?

Answer 1

Answer:

$x=\frac{-5\pm \sqrt{57}}{2}$ i.e. x= 1.3 and x= -6.3

Step-by-step explanation:

We are given the equation, $x^2 = -5x + 8$ i.e. $x^2+5x-8=0$

Now, as we know,

The solution of the quadratic equation [texa]x^2+bx+c=0[/tex] is given by $x=\frac{-b\pm \sqrt{b^{2}-4ac}}{2a}$.

On comparing, we have,

a= 1, b= 5 and c= -8

So, the solution of the given equation is,

$x=\frac{-5\pm \sqrt{5^{2}-4\times 1\times (-8)}}{2\times 1}$

i.e. $x=\frac{-5\pm \sqrt{5^{2}-4\times 1\times (-8)}}{2\times 1}$

i.e. $x=\frac{-5\pm \sqrt{25+32}}{2}$

i.e. $x=\frac{-5\pm \sqrt{57}}{2}$

i.e. $x=\frac{-5\pm 7.6}{2}$

i.e. $x=\frac{-5+7.6}{2}$ and i.e. $x=\frac{-5-7.6}{2}$

i.e. $x=\frac{2.6}{2}$ and i.e. $x=\frac{12.6}{2}$

i.e. x= 1.3 and x= -6.3

Thus, the solutions of the given equation are,

$x=\frac{-5\pm \sqrt{57}}{2}$ i.e. x= 1.3 and x= -6.3

Answer 2

Rewrite the equation set = to 0.
x^2 + 5x - 8 = 0
The quadratic will not factor so you have to use the quadratic formula.
x = (-b + - sqrt(b^2 - 4ac))/2a
x = (5 + - sqrt(25 - 4* 1* -8))/2
x = (5 + - sqrt 57)/2