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a+b=4
a x b = 2
a^2 + b^2 =?


Răspuns :


[tex]a + b = 4 \: \: \: | ^{2} \\ \\ {(a + b)}^{2} = {4}^{2} \\ \\ {a}^{2} + 2ab + {b}^{2} = 16 \\ \\ {a}^{2} + {b}^{2} = 16 - 2 \times 2 = 16 - 4 = 12 [/tex]

[tex] (a+b)^{2} [/tex]=[tex] a^{2} [/tex]+[tex] b^{2} [/tex]+2ab

[tex] (a+b)^{2} [/tex]=[tex] 4^{2} [/tex]=16

[tex] a^{2} [/tex]+[tex] b^{2} [/tex]=16-2ab=16-2*2=16-4=12