Question

If 3x² + kx +12=0 has equal roots then the value of k is​

Answer 1

k = ±12.

Explanation :-

Given :-

• Equation, 3x² + kx + 12 = 0
• Roots are real and equal.

To Find :-

• The value of k.

Solution :-

• Given, 3x² + kx + 12 = 0.

Compare with ax² + bx + c = 0 we get ,

=> a = 3 , b = k , c = 12

• Given, Roots are real and equal.

.°. Δ = 0

=> b² - 4ac = 0

=> (k)² - 4 × 3 × 12 = 0

=> k² - 144 = 0

=> k² = 144

=> k = ±12 .

Hence,

• The value of k is ±12.

Answer 2

Given ,

3(x) ² + kx +12=0 has equal roots

As we know that , if quadratic equation has equal roots , then

Discriminant = 0

$\sf \implies Discriminant = {(b)}^{2} - 4ac$

Thus ,

(k)² - 4 × 3 × 12 = 0

(k)² - 144 = 0

(k)² = 144

k = √144

k = ± 12

Therefore ,

• The value of k will be ± 12