Question

Explain why 7 x 11 x 13+13 and 7 x 6 x 5 x 4x3 x 2 x 1 +5 are composite numbers.​

Answer 1

Answer:

$\: \: \: \: \: 7 \times 11 \times 13 + 13 \\ = 13(7 \times 11 + 1) \\ = 13(77 + 1) \\ = 13 \times 78$

Since, 7×11×13+13 can be expressed as a product of two numbers. Therefore, it is a composite number.

Now,

$\: \: \: \: 7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1 + 5 \\ = 5(7 \times 6 \times 4 \times 3 \times 2 \times 1 + 1) \\ = 5(1008 + 1) \\ = 5 \times 1009$

Since 7×6×5×4×3×2×1+5 can be expressed as a product of two numbers. Therefore, it is a composite number.

Answer 2

this is the answer step by step....

these are composite no because of this

we can write, 7×11×13+13 = 13( 7×11+1)

= 13 × 78

and write second as 7× 6× 5× 4× 3 × 2 ×1 + 5

= 5 ( 7× 6× 4× 3 × 2×1 + 1)

= 5 ( 42 × 24 +1)

= 5 ( 1008 +1) = 5 ×1009

hope it is helpful to u

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