If `a+b+c = 5 and a^2+b^2+c^2 = 13`; find `ab+bc+ac`

If a + b + c = 13, a^2 + b^2 + c^2 = 69, " then find " ab + bc + ca .

If a+b+c=4 and a^(2)+b^(2)+c^(2)+3(ab+bc+ac)=21 where a, b, c in R then ab+bc+ca=

If A:B = 2:7 and B:C = 9:13, find A:C.

If a:b = 4:5 and b:c = 2:3, then a:c=_____.

If a:b=4:5 and b:c=2:3, then a:c=

If a+b+c=p and ab+bc+ac=q, find a^(2)+b^(2)+c^(2) .

If a+b+c=p and ab+bc+ac=q, find a^(2)+b^(2)+c^(2) .

If a:b=2:3 and b:c=5:7 then find a:c and a:b:c

If |{:(-a^2," "ab," "ac),(" "ab,-b^2," "bc),(" "ac," "bc,-c^2):}|=lambdaa^2b^2c^2, then find the value of lambda