Question

6. решите уравнение. а) (5х-2)(5х+-1)2=4; б) 100х2-16=0

Answer 1

$(5x-2)(5x+2)-(5x-1)^2=4 \\ 5x-1=t \\ (t-1)(t+3)-t^2=4 \\ t^2+3t-t-3-t^2=4 \\ t^2+2t-3-t^2=4\\ 2t-3=4 \\ 2t=7 \\ t=3,5 \\ 5x-1=3,5 \\ 5x=4,5 |:5 \\ x=0,9 \\$

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$100x^2-16=0 \\ (10x)^2-4^2=0 \\ (10x-4)(10x+4)=0 \\ 10x-4=0; 10x=4 |:10 ; x=0,4 \\ 10x+4=0; 10x=-4 :10; x=-0,4 \\$