Question

solve this quadratic equation by the method of completing square:- 3x² + 7x - 20 = 0​

Answer 1

Step-by-step explanation:

$3 {x}^{2} + 7x - 20 = 0 \\ \\ dividing \: by \: 3 \: we \: get.... \\ \\ {x}^{2} + \frac{7}{3} x - \frac{20}{3} = 0 \\ \\ third \: term = {( \frac{1}{2 } } \times coefficient \: of \: x) ^{2} \\ \\ = (\frac{1}{2} \times \frac{7}{3}) ( \frac{1}{2} \times \frac{7}{3} ) \\ \\ = ( \frac{7}{6} )( \frac{7}{6} ) \\ \\ = \frac{49}{36} \\ \\ adding \: on \: both \: sides.... \\ \\ {x}^{2} + \frac{7}{3} x + \frac{49}{36} = \frac{20}{3} + \frac{49}{36} \\ \\ {x}^{2} + \frac{7}{3} x + ( { \frac{7}{6} })^{2} = \frac{289}{36} \\ \\ {(x + \frac{7}{6} })^{2} = {( \frac{17}{6} })^{2} \\ \\ x + \frac{7}{6} = \frac{17}{6} \\ \\ x = \frac{17}{6} - \frac{7}{6} \\ \\ x = \frac{10}{6} \\ \\ x = \frac{5}{3}$

hope it helps...........✌✌

also .......x= -4 by -17/6 - 7/6= -4

Answer 2

Answer:

x = 5/3

Step-by-step explanation:

3x² + 7x- 20 = 0

dividing by 3 we get.......

x² + 7/3x - 20/3 =0

3rd term =(1/2 × coefficient of x)²

=(1/2 × 7/3) (1/2 × 7/3)

=(7/6) (7/6)

=49/36

adding on both sides......

x² + 7/3x + 49/36 = 20/3 + 49/36

x² + 7/3x + (7/6)² = 289/36

x + 7/6 = 17/6

x = 10/6

x = 5/3

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