One root of 3x² + kx − 8 = 0 is −2. Find k and the other root.

Question

Accepted Answer

k = 2, other root 4/3. Substituting x = −2: 3(4) + k(−2) − 8 = 0, so 4 − 2k = 0 and k = 2. Now solve 3x² + 2x − 8 = 0: x = -2 ± √4 + 966 = -2 ± 10/6 = 8/6 = 4/3 or −2. Reading the substitution as 4 + 2k = 0 gives the wrong sign k = −2.

One root of $3 x^{2} + k x - 8 = 0$ is −2. Find $k$ and the other root.

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More Class 10 The Quadratic Formula practice

One root of 3x2+kx−8=0 is −2. Find k and the other root.

Step-by-Step Solution

Master this chapter in 30 minutes a day.

More Class 10 The Quadratic Formula practice

One root of $3 x^{2} + k x - 8 = 0$ is −2. Find $k$ and the other root.