Question

с 385 по 394 плииииз.... .....

Answer 1

385. $10x^2+5x=0 \5x(2x+1)=0 \x(2x+1)=0 \ x=0; 2x+1=0 \ x=0; 2x=-1 \ x=0; x=-frac{1}{2}$
386. $12x^2+3x=0 \ 3x(4x+1)=0 \ x(4x+1)=0 \ x=0; 4x+1=0 \ x=0; 4x=-1 \ x=0; x=-frac{1}{4}$ 
387.  $25-100x^2=0 \ -25(2x-1)(2x+1)=0 \ (2x-1)(2x+1)=0 \ 2x=1; 2x=-1 \ x=frac{1}{2}; x=-frac{1}{2}$
388. $4-36x^2=0 \ -4(3x-1)(3x+1)=0 \ (3x-1)(3x+1)=0 \ 3x-1=0; 3x+1=0 \ 3x=1; 3x=-1 \ x=frac{1}{3}; x=-frac{1}{3}$ 
389. $2x^2-14=0 \ 2x^2=14 \ x^2=7 \ x=sqrt{7}; x=-sqrt{7}$ 
390. $3x^2-6=0 \3x^2=6 \ x^2=2 \ x=sqrt{2}; x=-sqrt{2}$ 
391. $2x^2-8=0 \ 2(x-2)x+2)=0 \ (x-2)(x+2)=0 \ x-2=0; x+2=0 \ x=2; x = -2$ 
392. $3x^2-75=0 \ 3 (x-5)(x+5)=0 \ (x-5)(x+5)=0 \ x-5=0; x+5=0 \ x=5; x=-5$ 
393. $4x^2-12=0 \ 4x^2=12 \ x^2=3 \ x=sqrt{3}; x=-sqrt{3}$ 
394. $3x^2-15=0 \ 3x^2=15 \ x^2=5 \ x =sqrt{5}; x=-sqrt{5}$