Question

Using quadratic formula solve the quadratic equation 18x2 + 9x – 20 = 0.​

Answer 1

Given :- Using quadratic formula solve the quadratic equation 18x² + 9x – 20 = 0.

Solution :-

we know that, Sridharacharya formula for Solving Quadratic Equation ax² +bx + c = 0 says that,

→ x = [ -b±√(b²-4ac) / 2a ]

or,

→ x = [ - b± √D /2a ] where D(Discriminant)= b²-4ac .

comparing the given quadratic equation 18x² + 9x – 20 = 0 with ax² +bx + c = 0 , we get,

• a = 18
• b = 9
• c = (-20)

Putting values we get,

→ D = b² - 4ac

→ D = (-20)² - 4*18*9

→ D = 400 - 648

→ D = (-248)

→ D = (-1 * 4 * 62)

Putting all values now, we get,

→ x = [ - b± √D /2a ]

→ x = [ - 9 ± √(-1 * 4 * 62) ] / 2 * 18

→ x = [ - 9 ± 2*√62*√(-1) ] / 36

→ x = [ - 9 ± 2i√(62) ] / 36 (Ans.) { √(-1) = i (iota) } .

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