Question

Here, find out the value of x

$\qquad\qquad\sf: 4x^2+20x-5=0$​

Answer 1

Given :-

$\qquad\qquad\sf 4x^2+20x-5=0$

Need To Find Out :-

• Value of x

Solution :-

According to the question -

• a=4,
• b=20
• c=-5

Using quadratic formula :-

$\qquad\qquad\sf:\implies x=\dfrac {-b\underline{+}\sqrt {b^2-4ac}}{2a}$

$\qquad\qquad\sf:\implies x=\dfrac {-20\underline{+}\sqrt {(20)^2-4×4×-5}}{2\times 4}$

$\qquad\qquad\sf:\implies x=\dfrac {-20\underline{+}\sqrt {400+80}}{8}$

$\qquad\qquad\sf:\implies x=\dfrac {-20\underline{+}\sqrt {480}}{8}$

$\qquad\qquad\sf:\implies x=\dfrac{-5\underline{+}\sqrt {480}}{2}$

$\qquad\qquad\sf\red {:\implies x=\dfrac {-5}{2}+\dfrac {1}{2}\sqrt {30}\quad or\quad \dfrac {-5}{2}-\dfrac {1}{2}\sqrt {30}}$

Answer 2

Answer:

Solving 4x2-20x-5 = 0 by the Quadratic Formula .

According to the Quadratic Formula, x , the solution for Ax2+Bx+C = 0 , where A, B and C are numbers, often called coefficients, is given by :

- B ± √ B2-4AC

x = ————————

2A

In our case, A = 4

B = -20

C = -5

Accordingly, B2 - 4AC =

400 - (-80) =

480

Applying the quadratic formula :

20 ± √ 480

x = ——————

8

so, here we get two solutions :

x = 20 - √480 = 5 - √ 30 = - 0.239

8. 2

x = 20 +√480 = 5 + √ 30 = 5.239

8. 2

Hope that helps you....