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2\left(x^{2}+6\right)-21=3\left(x+15\right)
Me whakarea ngā taha e rua o te whārite ki te 6, arā, te tauraro pātahi he tino iti rawa te kitea o 3,2.
2x^{2}+12-21=3\left(x+15\right)
Whakamahia te āhuatanga tohatoha hei whakarea te 2 ki te x^{2}+6.
2x^{2}-9=3\left(x+15\right)
Tangohia te 21 i te 12, ka -9.
2x^{2}-9=3x+45
Whakamahia te āhuatanga tohatoha hei whakarea te 3 ki te x+15.
2x^{2}-9-3x=45
Tangohia te 3x mai i ngā taha e rua.
2x^{2}-9-3x-45=0
Tangohia te 45 mai i ngā taha e rua.
2x^{2}-54-3x=0
Tangohia te 45 i te -9, ka -54.
2x^{2}-3x-54=0
Hurinahatia te pūrau ki te āhua tānga ngahuru. Whakaraupapahia ngā kīanga tau mai i te pū teitei rawa ki te mea iti rawa.
a+b=-3 ab=2\left(-54\right)=-108
Hei whakaoti i te whārite, whakatauwehea te taha mauī mā te whakarōpū. Tuatahi, me tuhi anō te taha mauī hei 2x^{2}+ax+bx-54. Hei kimi a me b, whakaritea tētahi pūnaha kia whakaoti.
1,-108 2,-54 3,-36 4,-27 6,-18 9,-12
I te mea kua tōraro te ab, he tauaro ngā tohu o a me b. I te mea kua tōraro te a+b, he nui ake te uara pū o te tau tōraro i tō te tōrunga. Whakarārangitia ngā tau tōpū takirua pērā katoa ka hoatu i te hua -108.
1-108=-107 2-54=-52 3-36=-33 4-27=-23 6-18=-12 9-12=-3
Tātaihia te tapeke mō ia takirua.
a=-12 b=9
Ko te otinga te takirua ka hoatu i te tapeke -3.
\left(2x^{2}-12x\right)+\left(9x-54\right)
Tuhia anō te 2x^{2}-3x-54 hei \left(2x^{2}-12x\right)+\left(9x-54\right).
2x\left(x-6\right)+9\left(x-6\right)
Tauwehea te 2x i te tuatahi me te 9 i te rōpū tuarua.
\left(x-6\right)\left(2x+9\right)
Whakatauwehea atu te kīanga pātahi x-6 mā te whakamahi i te āhuatanga tātai tohatoha.
x=6 x=-\frac{9}{2}
Hei kimi otinga whārite, me whakaoti te x-6=0 me te 2x+9=0.
2\left(x^{2}+6\right)-21=3\left(x+15\right)
Me whakarea ngā taha e rua o te whārite ki te 6, arā, te tauraro pātahi he tino iti rawa te kitea o 3,2.
2x^{2}+12-21=3\left(x+15\right)
Whakamahia te āhuatanga tohatoha hei whakarea te 2 ki te x^{2}+6.
2x^{2}-9=3\left(x+15\right)
Tangohia te 21 i te 12, ka -9.
2x^{2}-9=3x+45
Whakamahia te āhuatanga tohatoha hei whakarea te 3 ki te x+15.
2x^{2}-9-3x=45
Tangohia te 3x mai i ngā taha e rua.
2x^{2}-9-3x-45=0
Tangohia te 45 mai i ngā taha e rua.
2x^{2}-54-3x=0
Tangohia te 45 i te -9, ka -54.
2x^{2}-3x-54=0
Ko ngā whārite katoa o te āhua ax^{2}+bx+c=0 ka taea te whakaoti mā te whakamahi i te tikanga tātai pūrua: \frac{-b±\sqrt{b^{2}-4ac}}{2a}. E rua ngā otinga ka puta i te tikanga tātai pūrua, ko tētahi ina he tāpiri a ±, ā, ko tētahi ina he tango.
x=\frac{-\left(-3\right)±\sqrt{\left(-3\right)^{2}-4\times 2\left(-54\right)}}{2\times 2}
Kei te āhua arowhānui tēnei whārite: ax^{2}+bx+c=0. Me whakakapi 2 mō a, -3 mō b, me -54 mō c i te tikanga tātai pūrua, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-\left(-3\right)±\sqrt{9-4\times 2\left(-54\right)}}{2\times 2}
Pūrua -3.
x=\frac{-\left(-3\right)±\sqrt{9-8\left(-54\right)}}{2\times 2}
Whakareatia -4 ki te 2.
x=\frac{-\left(-3\right)±\sqrt{9+432}}{2\times 2}
Whakareatia -8 ki te -54.
x=\frac{-\left(-3\right)±\sqrt{441}}{2\times 2}
Tāpiri 9 ki te 432.
x=\frac{-\left(-3\right)±21}{2\times 2}
Tuhia te pūtakerua o te 441.
x=\frac{3±21}{2\times 2}
Ko te tauaro o -3 ko 3.
x=\frac{3±21}{4}
Whakareatia 2 ki te 2.
x=\frac{24}{4}
Nā, me whakaoti te whārite x=\frac{3±21}{4} ina he tāpiri te ±. Tāpiri 3 ki te 21.
x=6
Whakawehe 24 ki te 4.
x=-\frac{18}{4}
Nā, me whakaoti te whārite x=\frac{3±21}{4} ina he tango te ±. Tango 21 mai i 3.
x=-\frac{9}{2}
Whakahekea te hautanga \frac{-18}{4} ki ōna wāhi pāpaku rawa mā te tango me te whakakore i te 2.
x=6 x=-\frac{9}{2}
Kua oti te whārite te whakatau.
2\left(x^{2}+6\right)-21=3\left(x+15\right)
Me whakarea ngā taha e rua o te whārite ki te 6, arā, te tauraro pātahi he tino iti rawa te kitea o 3,2.
2x^{2}+12-21=3\left(x+15\right)
Whakamahia te āhuatanga tohatoha hei whakarea te 2 ki te x^{2}+6.
2x^{2}-9=3\left(x+15\right)
Tangohia te 21 i te 12, ka -9.
2x^{2}-9=3x+45
Whakamahia te āhuatanga tohatoha hei whakarea te 3 ki te x+15.
2x^{2}-9-3x=45
Tangohia te 3x mai i ngā taha e rua.
2x^{2}-3x=45+9
Me tāpiri te 9 ki ngā taha e rua.
2x^{2}-3x=54
Tāpirihia te 45 ki te 9, ka 54.
\frac{2x^{2}-3x}{2}=\frac{54}{2}
Whakawehea ngā taha e rua ki te 2.
x^{2}-\frac{3}{2}x=\frac{54}{2}
Mā te whakawehe ki te 2 ka wetekia te whakareanga ki te 2.
x^{2}-\frac{3}{2}x=27
Whakawehe 54 ki te 2.
x^{2}-\frac{3}{2}x+\left(-\frac{3}{4}\right)^{2}=27+\left(-\frac{3}{4}\right)^{2}
Whakawehea te -\frac{3}{2}, te tau whakarea o te kīanga tau x, ki te 2 kia riro ai te -\frac{3}{4}. Nā, tāpiria te pūrua o te -\frac{3}{4} ki ngā taha e rua o te whārite. Mā konei e pūrua tika tonu ai te taha mauī o te whārite.
x^{2}-\frac{3}{2}x+\frac{9}{16}=27+\frac{9}{16}
Pūruatia -\frac{3}{4} mā te pūrua i te taurunga me te tauraro o te hautanga.
x^{2}-\frac{3}{2}x+\frac{9}{16}=\frac{441}{16}
Tāpiri 27 ki te \frac{9}{16}.
\left(x-\frac{3}{4}\right)^{2}=\frac{441}{16}
Tauwehea x^{2}-\frac{3}{2}x+\frac{9}{16}. Ko te tikanga pūnoa, ina ko x^{2}+bx+c he pūrua tika pūrua tika pū, ka taea taua mea te tauwehea i ngā wā katoa hei \left(x+\frac{b}{2}\right)^{2}.
\sqrt{\left(x-\frac{3}{4}\right)^{2}}=\sqrt{\frac{441}{16}}
Tuhia te pūtakerua o ngā taha e rua o te whārite.
x-\frac{3}{4}=\frac{21}{4} x-\frac{3}{4}=-\frac{21}{4}
Whakarūnātia.
x=6 x=-\frac{9}{2}
Me tāpiri \frac{3}{4} ki ngā taha e rua o te whārite.