OOOHHHHH

Let a=(4^673)+(673^4) and b=(4^929) +(929^4).Then ,which is true?

a is prime , b is composite a and b both are prime a and b ,both are composite b is prime, a is composite

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Abdullah Shahriar
Dec 31, 2014

4 673 4 ( m o d 10 ) 4^{673} \equiv 4 \pmod{10}

67 3 4 1 ( m o d 10 ) 673^4 \equiv 1 \pmod{10}

a = ( 4 673 ) + ( 67 3 4 ) 5 ( m o d 10 ) 0 ( m o d 5 ) c o m p o s i t e a=(4^{673})+(673^4) \equiv 5 \pmod{10} \equiv 0 \pmod{5} \Rightarrow \underline{composite}


4 929 4 ( m o d 10 ) 4^{929} \equiv 4 \pmod{10}

92 9 4 1 ( m o d 10 ) 929^{4} \equiv 1 \pmod{10}

b = ( 4 929 ) + ( 92 9 4 ) 5 ( m o d 10 ) 0 ( m o d 5 ) c o m p o s i t e b=(4^{929})+(929^4) \equiv 5 \pmod{10} \equiv 0 \pmod{5} \Rightarrow \underline{composite}

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...