MCQ
The binary operation $*$ is defined by $a * b = a^2 + b^2 + ab + 1,$ then $(2 * 3) * 2$ is equal to:
  • A
    $20$
  • B
    $40$
  • C
    $400$
  • $445$

Answer

Correct option: D.
$445$
Given: $a * b = a^2 + b^2 + ab + $1
$2 * 3 = 2^2 + 3^2 + 2 \times 3 + 1$
$= 4 + 9 + 6 + 1$
$= 20$
$(2 * 3) * 2 = 20 * 2$
$= 20^2 + 2^2 + 20 \times 2 + 1$
$= 400 + 4 + 40 + 1$
$= 445$

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