Toán Lớp 8: giải pt
5x(12+7)-3x(80x-5)=-100
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Toán Lớp 8: giải pt
5x(12+7)-3x(80x-5)=-100
Comments ( 1 )
5x (12 + 7) – 3x (80x – 5) = -100
<=> 5x . 19 – 240x^2 + 15x = -100
<=> 95x – 240x^2 + 15x = -100
<=> -240x^2 + 110x + 100 = 0
<=> -24x^2 + 11x + 10 =0
<=> 24x^2 – 11x – 10 =0
<=> 24 (x^2 – 11/24x + 121/2304) – 1081/96 = 0
<=> 24 (x – 11/48)^2 – 1081/96=0
<=> 24(x-11/48)^2 = 1081/96
<=> (x-11/48)^2 = 1081/2304
<=> (x-11/48)^2 = ((+- \sqrt{1081})/48)^2
<=>x – 11/48 = (\sqrt{1081})/48 hoặc x- 11/48 = (- \sqrt{1081})/48
+) x – 11/48 = (\sqrt{1081})/48
<=> x= (\sqrt{1081} + 11)/48
+) x- 11/48 = (- \sqrt{1081})/48
<=> x = (11 – \sqrt{1081})/48
Vậy phương trình đã cho có tập nghiệm S = { (\sqrt{1081} + 11)/48 ; (11 – \sqrt{1081})/48 }