Question

1)daca x=5 si a+b=13 calculati:
a)3×x+7×a+7×b
b)10×x+(4×a+4×b)
c)x×a+x×b-50
d)(4×a+4×b-2×x)×(2×a+2×b+x)
2)calculati
a)ab+ac stiind că b+c=50 si a=2
b)ab-ac stiind că a=7 si b-c=100

Answer 1

x = 5 si a + b = 13

a)   3 × X + 7 × a + 7 × b = 3 × 5 + 7 × ( a + b ) = 15 + 7 × 13 = 15 + 91 = 106

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b) 10 × X + ( 4 × a + 4 × b ) = 10 × 5 + 4 × ( a + b ) = 50 + 4 × 13 = 50 + 52 = 102

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c)   X × a + X × b - 50 = X × ( a + b ) - 50 = 5 × 13 - 50 = 65 - 50 = 15

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d )   ( 4 × a + 4 × b - 2 × X ) × ( 2 × a + 2 × b + X ) = 1 302

= [ 4 × ( a + b ) - 2 × 5 ] × [ 2 × ( a + b ) + 5 ] =

= ( 4 × 13 - 10 ) × ( 2 × 13 + 5 ) =

= ( 52 - 10 ) × ( 26 + 5 ) =

= 42 × 31 =

= 1 302

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2 )

a)  ab + ac = a × ( b + c ) = 2 × 50 = 100

b)  ab - ac = a × ( b - c ) = 7 × 100 = 700