Question

find the roots of x²-3x-4=0 by using formula method​

Answer 1

Given :-

We have to find the roots of the Quadratic equation x²-3x -4 by Formula method

Quadratic formula :-

$\dfrac{ - b \pm \sqrt{ {b}^{2} - 4ac } }{2a}$

SOLUTION:-

x² - 3x - 4 comparing with ax² + bx + c

• a = 1
• b = -3
• c = -4

Substituting values in formula

$\dfrac{ - b \pm \sqrt{ {b}^{2} - 4ac } }{2a}$

$\dfrac{ - (-3) \pm \sqrt{ {(-3)}^{2} - 4(1)(-4) } }{2(1)}$

$\dfrac{ 3 \pm  \sqrt{ 9 +16 } }{2}$

$\dfrac{ 3 \pm \sqrt{ 25 } }{2}$

$\dfrac{3 \pm 5 }{2}$

$\dfrac{3+5}{2}$ , $\dfrac{3-5}{2}$

$\dfrac{8}{2}$ , $\dfrac{-2}{2}$

= ${4 , -1}$

So, the roots of Quadratic equation is 4 , -1

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Know more :-

• A Quadratic equatuion is one type of equation whose degree is 2
• A Quadratic equation has 2 roots
• We can find the two roots by various methods like complete squaring, factorisation etc
• The nature of two roots is determined by its Discriminant
• Discriminant of Quadratic equation is b²-4ac