Question

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y^2+1,4y+0,49−4y^2=0
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Answer 1

$\displaystyle \tt y^2+1,4y+0,49-4y^2=0\\\displaystyle \tt -3y^2+1,4y+0,49=0 \: \: \: \: \: | \cdot(-100)\\\displaystyle \tt 300y^2-140y-49=0\\\displaystyle \tt 300y^2-210y+70y-49=0\\\displaystyle \tt 30y(10y-7)+7(10y-7)=0\\\displaystyle \tt (10y-7)(30y+7)=0\\\\ \displaystyle \tt 10y-7=0\\\displaystyle \tt 10y=7\\\displaystyle \tt y=7\div10\\\displaystyle \tt \bold{y_1=0,7}\\\\ \displaystyle \tt 30y+7=0\\\displaystyle \tt 30y=-7\\\displaystyle \tt \bold{y_2=-\frac{7}{30}}$