document.write( "Question 1049379: 1)In 3d-space, let v1=(0,2,1) v2=(2,1,1) v3=(1,3,-1) v4=(4,2,1). Write v4 as linear combination of v1,v2,v3.\r
\n" ); document.write( "\n" ); document.write( "2)let v1=(0,-4,7) and v2=(3,-2,-1)
\n" ); document.write( "find
\n" ); document.write( "i)length of v1
\n" ); document.write( "ii) v1+v2
\n" ); document.write( "iii)length of v1+v2
\n" ); document.write( "iv)angle between v1 and v2
\n" ); document.write( "v)v1.v2
\n" ); document.write( "vi)v1xv2
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Algebra.Com's Answer #664932 by Fombitz(32388)\"\" \"About 
You can put this solution on YOUR website!
1.(4,2,1)=a(0,2,1)+b(2,1,1)+c(1,3,-1)
\n" ); document.write( "(4,2,1)=(0a+2b+c,2a+b+3c,a+b-c)
\n" ); document.write( "Using Cramer's rule,
\n" ); document.write( "\"A=%28matrix%283%2C3%2C%0D%0A0%2C2%2C1%2C%0D%0A2%2C1%2C3%2C%0D%0A1%2C1%2C-1%29%29\"
\n" ); document.write( "\"abs%28A%29=11\"
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\n" ); document.write( "\"A%5Ba%5D=%28matrix%283%2C3%2C%0D%0A4%2C2%2C1%2C%0D%0A2%2C1%2C3%2C%0D%0A1%2C1%2C-1%29%29\"
\n" ); document.write( "\"abs%28A%5Ba%5D%29=-5\"
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\n" ); document.write( "\"A%5Bb%5D=%28matrix%283%2C3%2C%0D%0A0%2C4%2C1%2C%0D%0A2%2C2%2C3%2C%0D%0A1%2C1%2C-1%29%29\"
\n" ); document.write( "\"abs%28A%5Bb%5D%29=20\"
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\n" ); document.write( "\"A%5Bc%5D=%28matrix%283%2C3%2C%0D%0A0%2C2%2C4%2C%0D%0A2%2C1%2C2%2C%0D%0A1%2C1%2C1%29%29\"
\n" ); document.write( "\"abs%28A%5Bc%5D%29=4\"
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\n" ); document.write( "\"a=abs%28A%5Ba%5D%29%2Fabs%28A%29=-5%2F11\"
\n" ); document.write( "\"b=abs%28A%5Bb%5D%29%2Fabs%28A%29=20%2F11\"
\n" ); document.write( "\"c=abs%28A%5Bc%5D%29%2Fabs%28A%29=4%2F11\"
\n" ); document.write( "So then,
\n" ); document.write( "(4,2,1)=(-5/11)*(0,2,1)+(20/11)*(2,1,1)+(4/11)*(1,3,-1)
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\n" ); document.write( "2.i) \"abs%28V%5B1%5D%29=sqrt%280%5E2%2B%28-4%29%5E2%2B7%5E2%29\"
\n" ); document.write( "ii) V[1]+V[2]=(0+3,-4-2,7-1)=(3,-6,6)
\n" ); document.write( "iii)\"abs%28V%5B1%5D%2BV%5B2%5D%29=sqrt%283%5E2%2B%28-6%29%5E2%2B6%5E2%29\"
\n" ); document.write( "iv) Use the dot product,
\n" ); document.write( "\"V%5B1%5D%2AV%5B2%5D=0%2A3%2B%28-4%29%28-2%29%2B7%28-1%29=8-7=1\"
\n" ); document.write( "\"cos%28theta%29=%28V%5B1%5D%2AV%5B2%5D%29%2F%28abs%28V%5B1%5D%29abs%28V%5B2%5D%29%29\"
\n" ); document.write( "\"abs%28V%5B2%5D%29=sqrt%283%5E2%2B%28-2%29%5E2%2B%28-1%29%5E2%29\"
\n" ); document.write( "Plug in the values to get the answer.
\n" ); document.write( "v) From previous, \"V%5B1%5D%2AV%5B2%5D=1\"
\n" ); document.write( "vi)
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\n" ); document.write( "\"V%5B1%5DxV%5B2%5D=%28matrix%281%2C3%2C%0D%0A18%2C21%2C12%29%29\"
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